Ionizing radiation stable thermoplastic composition, method of making, and articles formed therefrom

ABSTRACT

A thermoplastic composition comprises a sulfonate end-capped polycarbonate of formula:
 
Z-S(O) 2 —O-(-L-) m -O—S(O) 2 -Z
 
wherein each Z is independently an alkyl or aryl group, wherein -(-L-) m - is a polycarbonate linking group with m units of linking unit L, and wherein m is at least one. Methods of making the sulfonate end-capped polycarbonate and thermoplastic composition, and articles prepared therefrom, are also disclosed.

BACKGROUND OF THE INVENTION

This disclosure relates to stabilized thermoplastic compositions,methods of manufacture, and articles and uses thereof.

Irradiation using electron beam (e-beam) radiation or gamma ray (γ-ray)radiation (also referred to as “gamma radiation”) is increasingly usedto sterilize lightweight or disposable plastic articles for use inhospitals, biological laboratories, manufacturers of medical devices,and other end-users of sterile equipment. Gamma ray sources such as, forexample, ⁶⁰Co, which emits a β-particle and gamma ray radiation at 1.17and 1.33 megaelectron volts (MeV), can be used for sterilization. Someadvantages of gamma ray radiation are that it is more penetrating thanE-beam radiation, leaves no residue, and can be less damaging toplastics than heat and/or moisture. Because of the ability of gamma raysto penetrate plastics, articles that have already been packaged and/orassembled may conveniently be sterilized. Further, use of such radiationis ideal for sterilizing large numbers of articles, such as those madefrom plastics, due to the penetrating ability of gamma radiation,wherein the units closer to the source can receive a similar dose tothose furthest from the source. Articles such as blood bags, petridishes, syringes, beakers, vials, centrifuge tubes, spatulas, and thelike, as well as prepackaged articles, are desirably sterilized usingthis method.

Thermoplastics are useful for preparing articles such as those listedabove. In particular, polycarbonates, with their balance of propertiesincluding transparency, low color, impact resistance, ductility, andmelt flow, are desirable for use as materials of construction. However,exposure of polycarbonates to gamma ray doses suitable for sterilization(typically nominal doses of 10 to 85 kiloGrays (kGy), where 1 Grayequals 1 Joule of absorbed energy per kilogram of mass) can result inobservable yellowing of the polycarbonate, and may further result in thedegradation of one or more mechanical properties. Stabilizers, alsoreferred to in the art as “antirads”, may be used to mitigate theeffects of the gamma ray dose on plastics generally. Stabilizers presentin amounts sufficient to reduce yellowing in thermoplastic compositionscomprising polycarbonates may also affect one or more of the desirablemechanical properties of the thermoplastic composition, such as, forexample, impact strength and/or ductility. The usefulness of stabilizersto reduce yellowing in thermoplastic compositions of polycarbonate upongamma ray exposure can, in this way, be mitigated by these secondaryconsiderations of mechanical properties. Colorants may be added in orderto offset the yellowness resulting from sterilization of polycarbonatecompositions. However, because the amount of colorant added to thepolycarbonate is often selected for a given radiation dose, exposuredose variations due to process variability or re-sterilization cancreate color differences that may be noticeable to the eye.

There accordingly remains a need in the art for improved stabilizers forpolycarbonate compositions, as well as polycarbonate compositions havingimproved resistance to gamma ray radiation.

SUMMARY OF THE INVENTION

The above deficiencies in the art are alleviated by, in an embodiment, athermoplastic composition comprising a sulfonate end-cappedpolycarbonate of formula:Z-S(O)₂—O-(-L-)_(m)-O—S(O)₂-Zwherein each Z is independently an alkyl or aryl group, wherein-(-L-)_(m)- is a polycarbonate linking group with m units of linkingunit L.

In another embodiment, a thermoplastic composition comprising asulfonate end-capped polycarbonate of formula:Z-S(O)₂—O-(-L-)_(m)-O—S(O)₂-Zwherein each Z is independently an alkyl or aryl group, wherein-(-L-)_(m)- is a polycarbonate linking group with m units of linkingunit L, and wherein m is at least one; wherein a molded article having athickness of 3.2±0.12 millimeters and consisting of the sulfonateend-capped polycarbonate, a polycarbonate resin, and an effective amountof each of an aliphatic diol, a mold-release agent, and an antioxidanthas, after exposure to a total gamma radiation dose of 83 kGy and whenmeasured according to ASTM D1925-70, an increase in yellowness index(dYI) of less than or equal to 36, when compared to the unexposedarticle.

In another embodiment, a thermoplastic composition comprises a sulfonateend-capped polycarbonate of formula:Z-S(O)₂—O-(-L-)_(m)-O—S(O)₂-Zwherein each Z is independently an alkyl or aryl group, and -(-L-)_(m)-is a polycarbonate linking group with m units of linking unit L, whereinm is at least one; and a polycarbonate, wherein the sulfonate end-cappedpolycarbonate is present in an amount of 0.1 to 100 wt %, based on thetotal weight of the sulfonate end-capped polycarbonate and any addedpolycarbonate, with the proviso that the amount and type of sulfonateend-capped polycarbonate used is selected so that the overallconcentration of sulfonate end groups is not greater than a molarconcentration of 500 millimoles per kilogram (mmol/Kg), and is not lessthan 0.001 mmol/Kg, of the total weight of the thermoplasticcomposition.

In another embodiment, a thermoplastic composition comprises a sulfonateend-capped polycarbonate of formula:Z-S(O)₂—O-(-L-)_(m)-O—S(O)₂-Zwherein each Z is independently an alkyl or aryl group, and -(-L-)_(m)-is a polycarbonate linking group with m units of linking unit L, whereinm is at least one; and a polycarbonate, wherein a molded article havinga thickness of 3.2±0.12 millimeters and consisting of the sulfonateend-capped polycarbonate, the polycarbonate, and an effective amount ofeach of an aliphatic diol, a mold-release agent, and an antioxidant has,after exposure to a total gamma radiation dose of 83 kGy and whenmeasured according to ASTM D1925-70, an increase in yellowness index(dYI) of less than or equal to 36, when compared to the unexposedarticle.

In another embodiment, a method of preparing a sulfonate end-cappedpolycarbonate comprising condensing a dihydroxy compound, a reactivesulfonic acid derivative, and an activated carbonyl compound, in abiphasic medium at a pH of about 9 to about 11, and in the presence of aphase transfer catalyst having the formula (R)₄Q⁺X, wherein each R isthe same or different, and is a C₁₋₁₀ alkyl group; Q is a nitrogen orphosphorus atom; and X is a halogen atom or a C₁₋₈ alkoxy group or C₆₋₁₈aryloxy group.

In another embodiment, a method of forming a thermoplastic compositioncomprises melt blending a sulfonate end-capped polycarbonate of formula:Z-S(O)₂—O-(-L-)_(m)-O—S(O)₂-Zwherein each Z is independently an alkyl or aryl group, and -(-L-)_(m)-is a polycarbonate linking group with m units of linking unit L, whereinm is at least one; and a polycarbonate, wherein a molded article havinga thickness of 3.2±0.12 millimeters and consisting of the sulfonateend-capped polycarbonate, the polycarbonate, and an effective amount ofeach of an aliphatic diol, a mold-release agent, and an antioxidant has,after exposure to a total gamma radiation dose of 83 kGy and whenmeasured according to ASTM D1925-70, an increase in yellowness index(dYI) of less than or equal to 36, when compared to the unexposedarticle.

In another embodiment, an article comprising the thermoplasticcomposition is disclosed.

The above described and other features are exemplified by the followingdetailed description.

DETAILED DESCRIPTION OF THE INVENTION

Surprisingly, it has been found that a thermoplastic compositioncomprising a sulfonate end-capped polycarbonate has significantlyimproved resistance to yellowing upon exposure to gamma radiation. Theuse of the sulfonate end-capped polycarbonate helps maintain themechanical properties at the same or comparable level as an unstabilizedthermoplastic composition comprising polycarbonate. The sulfonateend-capped polycarbonate can be used alone or in combination with apolycarbonate.

As used herein, the term “alkyl” refers to a straight or branched chainmonovalent hydrocarbon group; “alkylene” refers to a straight orbranched chain divalent hydrocarbon group; “alkylidene” refers to astraight or branched chain divalent hydrocarbon group, with bothvalences on a single common carbon atom; “alkenyl” refers to a straightor branched chain monovalent hydrocarbon group having at least twocarbons joined by a carbon-carbon double bond; “cycloalkyl” refers to anon-aromatic monovalent monocyclic or multicylic hydrocarbon grouphaving at least three carbon atoms, “cycloalkylene” refers to anon-aromatic alicyclic divalent hydrocarbon group having at least threecarbon atoms, with at least one degree of unsaturation; “aryl” refers toan aromatic monovalent group containing only carbon in the aromatic ringor rings; “arylene” refers to an aromatic divalent group containing onlycarbon in the aromatic ring or rings; “alkylaryl” refers to an arylgroup that has been substituted with an alkyl group as defined above,with 4-methylphenyl being an exemplary alkylaryl group; “arylalkyl”refers to an alkyl group that has been substituted with an aryl group asdefined above, with benzyl being an exemplary arylalkyl group; “acyl”refers to a an alkyl group as defined above with the indicated number ofcarbon atoms attached through a carbonyl carbon bridge (—C(═O)—);“alkoxy” refers to an alkyl group as defined above with the indicatednumber of carbon atoms attached through an oxygen bridge (—O—); and“aryloxy” refers to an aryl group as defined above with the indicatednumber of carbon atoms attached through an oxygen bridge (—O—).

Unless otherwise indicated, each of the foregoing groups may beunsubstituted or substituted, provided that the substitution does notsignificantly adversely affect synthesis, stability, or use of thecompound. The term “substituted” as used herein means that any one ormore hydrogens on the designated atom or group is replaced with anothergroup, provided that the designated atom's normal valence is notexceeded. When the substituent is oxo (i.e., ═O), then two hydrogens onthe atom are replaced. Combinations of substituents and/or variables arepermissible provided that the substitutions do not significantlyadversely affect synthesis or use of the compound.

The thermoplastic composition can comprise a polycarbonate. As usedherein, the terms “polycarbonate” and “polycarbonate resin” meanscompositions having repeating structural carbonate units of the formula(1):

in which at least 60 percent of the total number of R¹ groups arearomatic organic radicals and the balance thereof are aliphatic,alicyclic, or aromatic radicals. In one embodiment, each R¹ is anaromatic organic radical. In another embodiment, each R¹ is a radical ofthe formula (2):-A¹-Y¹-A²-  (2)wherein each of A¹ and A² is a monocyclic divalent aryl radical and Y¹is a bridging radical having one or two atoms that separate A¹ from A².In an exemplary embodiment, one atom separates A¹ from A². Illustrativenon-limiting examples of radicals of this type are —O—, —S—, —S(O)—,—S(O₂)—, —C(O)—, methylene, cyclohexyl-methylene,2-[2.2.1]-bicycloheptylidene, ethylidene, isopropylidene,neopentylidene, cyclohexylidene, cyclopentadecylidene,cyclododecylidene, and adamantylidene. The bridging radical Y¹ may be ahydrocarbon group or a saturated hydrocarbon group such as methylene,cyclohexylidene, or isopropylidene. In another embodiment, Y¹ is acarbon-carbon bond (—) connecting A¹ and A².

Polycarbonates may be produced by the interfacial reaction of dihydroxycompounds having the formula HO—R¹—OH, which includes dihydroxy aromaticcompounds of formula (3):HO-A¹-Y¹-A²-OH  (3)wherein Y¹, A¹ and A² are as described above. Also included arebisphenol compounds of general formula (4):

wherein R^(a) and R^(b) each represent a halogen atom or a monovalenthydrocarbon group and may be the same or different; p and q are eachindependently integers of 0 to 4; and X^(a) represents one of the groupsof formula (5):

wherein R^(c) and R^(d) each independently represent a hydrogen atom ora monovalent linear alkyl or cyclic alkylene group and R^(e) is adivalent hydrocarbon group. In an embodiment, R^(c) and R^(d) representa cyclic alkylene group comprising carbon atoms, heteroatoms with avalency of two or greater, or a combination comprising at least oneheteroatom and at least two carbon atoms. Suitable heteroatoms include—O—, —S—, and —N(Z)-, where Z is a substituent group selected fromhydrogen, halogen, hydroxy, C₁₋₁₂ alkyl, C₁₋₁₂ alkoxy, or C₁₋₁₂ acyl.Where present, the cyclic alkylene group may have 3 to 20 atoms, and maybe a single saturated or unsaturated ring, or fused polycyclic ringsystem wherein the fused rings are saturated, unsaturated, or aromatic.

Suitable polycarbonates further include those derived from bisphenolscontaining alkyl cyclohexane units. Such polycarbonates have structuralunits corresponding to the formula (6):

wherein R^(a)-R^(d) are each independently hydrogen, C₁₋₁₂ alkyl, orhalogen; and substituents R_(e)-R_(i) and R_(e′)-R_(i′) are eachindependently hydrogen or C₁₋₁₂ alkyl. The substituents may be aliphaticor aromatic, straight-chain, cyclic, bicyclic, branched, saturated, orunsaturated. In a specific embodiment, alkyl cyclohexane-containingbisphenols, for example the reaction product of two moles of a phenolwith one mole of a hydrogenated isophorone, are useful for makingpolycarbonate polymers with high glass transition temperatures and highheat distortion temperatures. Such isophorone bisphenol-containingpolycarbonates correspond to formula (6), wherein each of R_(f), R_(f′),and R_(h) are methyl groups; R_(e), R_(e′), R_(g), R_(g′), R_(h′),R_(i), and R_(i′), are each hydrogen; and R_(a)-R_(d) are as definedabove. These isophorone bisphenol based polymers, includingpolycarbonate copolymers made containing non-alkyl cyclohexanebisphenols and blends of alkyl cyclohexyl bisphenol containingpolycarbonates with non-alkyl cyclohexyl bisphenol polycarbonates, aresupplied by Bayer Co. under the APEC® trade name.

Some illustrative, non-limiting examples of suitable dihydroxy compoundsinclude the following: 4,4′-dihydroxybiphenyl, 1,6-dihydroxynaphthalene,2,6-dihydroxynaphthalene, bis(4-hydroxyphenyl)methane,bis(4-hydroxyphenyl)diphenylmethane,bis(4-hydroxyphenyl)-1-naphthylmethane, 1,2-bis(4-hydroxyphenyl)ethane,1,1-bis(4-hydroxyphenyl)-1-phenylethane,2-(4-hydroxyphenyl)-2-(3-hydroxyphenyl)propane,bis(4-hydroxyphenyl)phenylmethane,2,2-bis(4-hydroxy-3-bromophenyl)propane,1,1-bis(hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)cyclohexane,1,1-bis(4-hydroxy-3 methyl phenyl)cyclohexane1,1-bis(4-hydroxyphenyl)isobutene,1,1-bis(4-hydroxyphenyl)cyclododecane,trans-2,3-bis(4-hydroxyphenyl)-2-butene,2,2-bis(4-hydroxyphenyl)adamantine, (alpha,alpha′-bis(4-hydroxyphenyl)toluene, bis(4-hydroxyphenyl)acetonitrile,2,2-bis(3-methyl-4-hydroxyphenyl)propane,2,2-bis(3-ethyl-4-hydroxyphenyl)propane,2,2-bis(3-n-propyl-4-hydroxyphenyl)propane,2,2-bis(3-isopropyl-4-hydroxyphenyl)propane,2,2-bis(3-sec-butyl-4-hydroxyphenyl)propane,2,2-bis(3-t-butyl-4-hydroxyphenyl)propane,2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane,2,2-bis(3-allyl-4-hydroxyphenyl)propane,2,2-bis(3-methoxy-4-hydroxyphenyl)propane,2,2-bis(4-hydroxyphenyl)hexafluoropropane,1,1-dichloro-2,2-bis(4-hydroxyphenyl)ethylene,1,1-dibromo-2,2-bis(4-hydroxyphenyl)ethylene,1,1-dichloro-2,2-bis(5-phenoxy-4-hydroxyphenyl)ethylene,4,4′-dihydroxybenzophenone, 3,3-bis(4-hydroxyphenyl)-2-butanone,1,6-bis(4-hydroxyphenyl)-1,6-hexanedione, ethylene glycolbis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)ether,bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)sulfoxide,bis(4-hydroxyphenyl)sulfone, 9,9-bis(4-hydroxyphenyl)fluorine,2,7-dihydroxypyrene,6,6′-dihydroxy-3,3,3′,3′-tetramethylspiro(bis)indane (“spirobiindanebisphenol”), 3,3-bis(4-hydroxyphenyl)phthalide,2,6-dihydroxydibenzo-p-dioxin, 2,6-dihydroxythianthrene,2,7-dihydroxyphenoxathin, 2,7-dihydroxy-9,10-dimethylphenazine,3,6-dihydroxydibenzofuran, 3,6-dihydroxydibenzothiophene, and2,7-dihydroxycarbazole, and the like, as well as combinations comprisingat least one of the foregoing dihydroxy compounds.

Specific examples of the types of bisphenol compounds represented byformula (3) include 1,1-bis(4-hydroxyphenyl)methane,1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane(hereinafter “bisphenol A” or “BPA”), 2,2-bis(4-hydroxyphenyl)butane,2,2-bis(4-hydroxyphenyl)octane, 1,1-bis(4-hydroxyphenyl)propane,1,1-bis(4-hydroxyphenyl)n-butane,2,2-bis(4-hydroxy-1-methylphenyl)propane,1,1-bis(4-hydroxy-t-butylphenyl)propane,3,3-bis(4-hydroxyphenyl)phthalimidine,2-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine (PPPBP), and1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (DMBPC). Combinationscomprising at least one of the foregoing dihydroxy compounds may also beused.

Another dihydroxy aromatic group R¹ is derived from a dihydroxy aromaticcompound of formula (7):

wherein each R^(f) is independently a halogen atom, a C₁₋₁₀ hydrocarbongroup, or a C₁₋₁₀ halogen substituted hydrocarbon group, and n is 0 to4. The halogen is usually bromine. Examples of compounds that may berepresented by the formula (7) include resorcinol, substitutedresorcinol compounds such as 5-methyl resorcinol, 5-ethyl resorcinol,5-propyl resorcinol, 5-butyl resorcinol, 5-t-butyl resorcinol, 5-phenylresorcinol, 5-cumyl resorcinol, 2,4,5,6-tetrafluoro resorcinol,2,4,5,6-tetrabromo resorcinol, or the like; catechol; hydroquinone;substituted hydroquinones such as 2-methyl hydroquinone, 2-ethylhydroquinone, 2-propyl hydroquinone, 2-butyl hydroquinone, 2-t-butylhydroquinone, 2-phenyl hydroquinone, 2-cumyl hydroquinone,2,3,5,6-tetramethyl hydroquinone, 2,3,5,6-tetra-t-butyl hydroquinone,2,3,5,6-tetrafluoro hydroquinone, 2,3,5,6-tetrabromo hydroquinone, orthe like; or combinations comprising at least one of the foregoingcompounds.

In a specific embodiment, the polycarbonate is a linear homopolymerderived from bisphenol A, in which each of A¹ and A² is p-phenylene andY¹ is isopropylidene. The polycarbonates may have an intrinsicviscosity, as determined in chloroform at 25° C., of 0.3 to 1.5deciliters per gram (dl/g), specifically 0.45 to 1.0 dl/g. Thepolycarbonates may have a weight average molecular weight (Mw) of 10,000to 100,000, as measured by gel permeation chromatography (GPC) using acrosslinked styrene-divinyl benzene column, at a sample concentration of1 milligram per milliliter, and as calibrated with polycarbonatestandards.

In an embodiment, the polycarbonate has flow properties suitable for themanufacture of thin articles. Melt volume flow rate (often abbreviatedMVR) measures the rate of extrusion of a thermoplastics through anorifice at a prescribed temperature and load. Polycarbonates suitablefor the formation of thin articles may have an MVR, measured at 300°C./1.2 kg according to ASTM D1238-04, of 0.5 to 80 cubic centimeters per10 minutes (cc/10 min). In a specific embodiment, a suitablepolycarbonate composition has an MVR measured at 300° C./1.2 kgaccording to ASTM D1238-04, of 0.5 to 50 cc/10 min, specifically 0.5 to25 cc/10 min, and more specifically 1 to 15 cc/10 min. Mixtures ofpolycarbonates of different flow properties may be used to achieve theoverall desired flow property.

The polycarbonate may have a light transmittance greater than or equalto 55%, specifically greater than or equal to 60% and more specificallygreater than or equal to 70%, as measured at 3.2 millimeters thicknessaccording to ASTM D1003-00. The polycarbonate may also have a haze lessthan or equal to 50%, specifically less than or equal to 40%, and mostspecifically less than or equal to 30%, as measured at 3.2 millimetersthickness according to ASTM D1003-00.

“Polycarbonates” and “polycarbonate resins” as used herein furtherinclude homopolycarbonates, copolymers comprising different R¹ moietiesin the carbonate (referred to herein as “copolycarbonates”), copolymerscomprising carbonate units and other types of polymer units, such asester units, and combinations comprising one or more ofhomopolycarbonates and copolycarbonates. As used herein, “combination”is inclusive of blends, mixtures, alloys, reaction products, and thelike. A specific type of copolymer is a polyester carbonate, also knownas a polyester-polycarbonate. Such copolymers further contain, inaddition to recurring carbonate chain units of the formula (1),repeating units of formula (8):

wherein D is a divalent radical derived from a dihydroxy compound, andmay be, for example, a C₂₋₁₀ alkylene radical, a C₆₋₂₀ alicyclicradical, a C₆₋₂₀ aromatic radical or a polyoxyalkylene radical in whichthe alkylene groups contain 2 to 6 carbon atoms, specifically 2, 3, or 4carbon atoms; and T divalent radical derived from a dicarboxylic acid,and may be, for example, a C₂₋₁₀ alkylene radical, a C₆₋₂₀ alicyclicradical, a C₆₋₂₀ alkyl aromatic radical, or a C₆₋₂₀ aromatic radical.

In one embodiment, D is a C₂₋₆ alkylene radical. In another embodiment,D is derived from an aromatic dihydroxy compound of formula (4) above.In another embodiment, D is derived from an aromatic dihydroxy compoundof formula (7) above.

Examples of aromatic dicarboxylic acids that may be used to prepare thepolyesters include isophthalic or terephthalic acid,1,2-di(p-carboxyphenyl)ethane, 4,4′-dicarboxydiphenyl ether,4,4′-bisbenzoic acid, and mixtures comprising at least one of theforegoing acids. Acids containing fused rings can also be present, suchas in 1,4-, 1,5-, or 2,6-naphthalenedicarboxylic acids. Specificdicarboxylic acids are terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexane dicarboxylic acid, or mixtures thereof. Aspecific dicarboxylic acid comprises a mixture of isophthalic acid andterephthalic acid wherein the weight ratio of terephthalic acid toisophthalic acid is 91:1 to 2:98. In another specific embodiment, D is aC₂₋₆ alkylene radical and T is p-phenylene, m-phenylene, naphthalene, adivalent cycloaliphatic radical, or a mixture thereof. This class ofpolyester includes the poly(alkylene terephthalates).

In addition to the ester units, the polyester-polycarbonates comprisecarbonate units as described hereinabove. Carbonate units of formula (1)may also be derived from aromatic dihydroxy compounds of formula (7),wherein specific carbonate units are resorcinol carbonate units.

Specifically, the polyester unit of a polyester-polycarbonate can bederived from the reaction of a combination of isophthalic andterephthalic diacids (or derivatives thereof) with resorcinol, bisphenolA, or a combination comprising at least one of these, wherein the molarratio of isophthalate units to terephthalate units is 91:9 to 2:98,specifically 85:15 to 3:97, more specifically 80:20 to 5:95, and stillmore specifically 70:30 to 10:90. The polycarbonate units can be derivedfrom resorcinol and/or bisphenol A, in a molar ratio of resorcinolcarbonate units to bisphenol A carbonate units of 0:100 to 99:1, and themolar ratio of the mixed isophthalate-terephthalate polyester units tothe polycarbonate units in the polyester-polycarbonate can be 1:99 to99:1, specifically 5:95 to 90:10, more specifically 10:90 to 80:20.Where a blend of polyester-polycarbonate with polycarbonate is used, theratio of polycarbonate to polyester-polycarbonate in the blend can be,respectively, 1:99 to 99:1, specifically 10:90 to 90:10.

The polyester-polycarbonates may have a weight-averaged molecular weight(Mw) of 1,500 to 100,000, specifically 1,700 to 50,000, and morespecifically 2,000 to 40,000. Molecular weight determinations areperformed using gel permeation chromatography (GPC), using a crosslinkedstyrene-divinylbenzene column and calibrated to polycarbonatereferences. Samples are prepared at a concentration of about 1 mg/ml,and are eluted at a flow rate of about 1.0 ml/min.

Suitable polycarbonates can be manufactured by processes such asinterfacial polymerization and melt polymerization. Although thereaction conditions for interfacial polymerization may vary, anexemplary process generally involves dissolving or dispersing a dihydricphenol reactant in aqueous caustic soda or potash, adding the resultingmixture to a suitable water-immiscible solvent medium, and contactingthe reactants with a carbonate precursor in the presence of a suitablecatalyst such as triethylamine or a phase transfer catalyst, undercontrolled pH conditions, e.g., 8 to 10. The most commonly used waterimmiscible solvents include methylene chloride, 1,2-dichloroethane,chlorobenzene, toluene, and the like. Suitable carbonate precursorsinclude, for example, a carbonyl halide such as carbonyl bromide orcarbonyl chloride, or a haloformate such as a bishaloformates of adihydric phenol (e.g., the bischloroformates of bisphenol A,hydroquinone, or the like) or a glycol (e.g., the bishaloformate ofethylene glycol, neopentyl glycol, polyethylene glycol, or the like).Combinations comprising at least one of the foregoing types of carbonateprecursors may also be used. A chain stopper (also referred to as acapping agent) may be included during polymerization. The chain-stopperlimits molecular weight growth rate, and so controls molecular weight inthe polycarbonate. A chain-stopper may be at least one of mono-phenoliccompounds, mono-carboxylic acid chlorides, and/or mono-chloroformates.Where a chain stopper is incorporated with the polycarbonate, the chainstopper may also be referred to as an end group.

For example, mono-phenolic compounds suitable as chain stoppers includemonocyclic phenols, such as phenol, C₁-C₂₂ alkyl-substituted phenols,p-cumyl-phenol, p-tertiary-butyl phenol, hydroxy diphenyl; monoethers ofdiphenols, such as p-methoxyphenol. Alkyl-substituted phenols includethose with branched chain alkyl substituents having 8 to 9 carbon atoms.A mono-phenolic UV absorber may be used as capping agent. Such compoundsinclude 4-substituted-2-hydroxybenzophenones and their derivatives, arylsalicylates, monoesters of diphenols such as resorcinol monobenzoate,2-(2-hydroxyaryl)-benzotriazoles and their derivatives,2-(2-hydroxyaryl)-1,3,5-triazines and their derivatives, and the like.Specifically, mono-phenolic chain-stoppers include phenol,p-cumylphenol, and/or resorcinol monobenzoate.

Mono-carboxylic acid chlorides may also be suitable as chain stoppers.These include monocyclic, mono-carboxylic acid chlorides such as benzoylchloride, C₁-C₂₂ alkyl-substituted benzoyl chloride, toluoyl chloride,halogen-substituted benzoyl chloride, bromobenzoyl chloride, cinnamoylchloride, 4-nadimidobenzoyl chloride, and mixtures thereof; polycyclic,mono-carboxylic acid chlorides such as trimellitic anhydride chloride,and naphthoyl chloride; and mixtures of monocyclic and polycyclicmono-carboxylic acid chlorides. Chlorides of aliphatic monocarboxylicacids with up to 22 carbon atoms are suitable. Functionalized chloridesof aliphatic monocarboxylic acids, such as acryloyl chloride andmethacryoyl chloride, are also suitable. Also suitable aremono-chloroformates including monocyclic, mono-chloroformates, such asphenyl chloroformate, alkyl-substituted phenyl chloroformate, p-cumylphenyl chloroformate, toluene chloroformate, and mixtures thereof.

Among the phase transfer catalysts that may be used in interfacialpolymerization are catalysts of the formula (R³)₄Q⁺X, wherein each R³ isthe same or different, and is a C₁₋₁₀ alkyl group; Q is a nitrogen orphosphorus atom; and X is a halogen atom or a C₁₋₈ alkoxy group or C₆₋₁₈aryloxy group. Suitable phase transfer catalysts include, for example,[CH₃(CH₂)₃]₄NX, [CH₃(CH₂)₃]₄PX, [CH₃(CH₂)₅]₄NX, [CH₃(CH₂)₆]₄NX,[CH₃(CH₂)₄]₄NX, CH₃[CH₃(CH₂)₃]₃NX, and CH₃[CH₃(CH₂)₂]₃NX, wherein X isCl⁻, Br⁻, a C₁₋₈ alkoxy group or a C₆₋₁₈ aryloxy group. In anembodiment, a specifically useful phase transfer catalyst isCH₃[CH₃(CH₂)₃]₃NCl (methyl tri-n-butyl ammonium chloride). An effectiveamount of a phase transfer catalyst may be 0.1 to 10 wt % based on theweight of bisphenol in the phosgenation mixture. In another embodimentan effective amount of phase transfer catalyst may be 0.5 to 2 wt %based on the weight of dihydroxy compound in the phosgenation mixture.

Alternatively, melt processes may be used to make the polycarbonates.Generally, in the melt polymerization process, polycarbonates may beprepared by co-reacting, in a molten state, the dihydroxy reactant(s)and a diaryl carbonate ester, such as diphenyl carbonate, in thepresence of a transesterification catalyst in a Banbury® mixer, twinscrew extruder, or the like to form a uniform dispersion. Volatilemonohydric phenol is removed from the molten reactants by distillationand the polymer is isolated as a molten residue. A specifically usefulmelt process for making polycarbonates uses a diaryl carbonate esterhaving electron withdrawing substituents on the aryls. Examples ofspecifically useful diaryl carbonate esters with electron withdrawingsubstituents include bis(4-nitrophenyl)carbonate,bis(2-chlorophenyl)carbonate, bis(4-chlorophenyl)carbonate, bis(methylsalicyl)carbonate, bis(4-methylcarboxylphenyl)carbonate,bis(2-acetylphenyl)carboxylate, bis(4-acetylphenyl)carboxylate, or acombination comprising at least one of these. In addition, suitabletransesterification catalyst for use may include phase transfercatalysts of formula (R³)₄Q⁺X above, wherein each R³, Q, and X are asdefined above. Examples of suitable transesterification catalystsinclude tetrabutylammonium hydroxide, tetrabutylammonium acetate,tetrabutylphosphonium hydroxide, tetrabutylphosphonium acetate,tetrabutylphosphonium phenolate, or a combination comprising at leastone of these.

Branched polycarbonates are also useful, as well as blends of a linearpolycarbonate and a branched polycarbonate. The branched polycarbonatesmay be prepared by adding a branching agent during polymerization. Thesebranching agents include polyfunctional organic compounds containing atleast three functional groups selected from hydroxyl, carboxyl,carboxylic anhydride, haloformyl, and mixtures of the foregoingfunctional groups. Specific examples include trimellitic acid,trimellitic anhydride, trimellitic trichloride, tris-p-hydroxy phenylethane, isatin-bis-phenol, tris-phenol TC(1,3,5-tris((p-hydroxyphenyl)isopropyl)benzene), tris-phenol PA(4(4(1,1-bis(p-hydroxyphenyl)-ethyl)alpha, alpha-dimethylbenzyl)phenol), 4-chloroformyl phthalic anhydride, trimesic acid, andbenzophenone tetracarboxylic acid. The branching agents may be added ata level of 0.05 to 2.0 wt % of the polycarbonate. All types ofpolycarbonate end groups are contemplated as being useful in thepolycarbonate, provided that such end groups do not significantly affectdesired properties of the thermoplastic compositions.

The polyester-polycarbonates may also be prepared by interfacialpolymerization. Rather than utilizing the dicarboxylic acid per se, itis possible, and sometimes even preferred, to employ the reactivederivatives of the acid, such as the corresponding dicarboxylic aciddihalides, in particular the dicarboxylic acid dichlorides and thedicarboxylic acid dibromides. Thus, for example instead of usingisophthalic acid, terephthalic acid, or mixtures thereof, it is possibleto employ isophthaloyl dichloride, terephthaloyl dichloride, andmixtures thereof.

In addition to the polycarbonates described above, combinations of thepolycarbonate with other thermoplastic polymers, for examplecombinations of homopolycarbonates and/or polycarbonate copolymers withpolyesters, may be used. Suitable polyesters may include, for example,polyesters having repeating units of formula (8), which includepoly(alkylene dicarboxylates), liquid crystalline polyesters, andpolyester copolymers. The polyesters described herein are generallycompletely miscible with the polycarbonates when blended.

The polyesters may be obtained by interfacial polymerization ormelt-process condensation as described above, by solution phasecondensation, or by transesterification polymerization wherein, forexample, a dialkyl ester such as dimethyl terephthalate may betransesterified with ethylene glycol using acid catalysis, to generatepoly(ethylene terephthalate). It is possible to use a branched polyesterin which a branching agent, for example, a glycol having three or morehydroxyl groups or a trifunctional or multifunctional carboxylic acidhas been incorporated. Furthermore, it is sometime desirable to havevarious concentrations of acid and hydroxyl end groups on the polyester,depending on the ultimate end use of the composition.

Useful polyesters may include aromatic polyesters, poly(alkylene esters)including poly(alkylene arylates), and poly(cycloalkylene diesters).Aromatic polyesters may have a polyester structure according to formula(8), wherein D and T are each aromatic groups as described hereinabove.In an embodiment, useful aromatic polyesters may include, for example,poly(isophthalate-terephthalate-resorcinol) esters,poly(isophthalate-terephthalate-bisphenol-A) esters,poly[(isophthalate-terephthalate-resorcinol)ester-co-(isophthalate-terephthalate-bisphenol-A)]ester, or acombination comprising at least one of these. Also contemplated arearomatic polyesters with a minor amount, e.g., from about 0.5 to about10 percent by weight, of units derived from an aliphatic diacid and/oran aliphatic polyol to make copolyesters.

Poly(alkylene arylates) may have a polyester structure according toformula (8), wherein T comprises groups derived from aromaticdicarboxylates, cycloaliphatic dicarboxylic acids, or derivativesthereof. Examples of specifically useful T groups include 1,2-, 1,3-,and 1,4-phenylene; 1,4- and 1,5-naphthylenes; cis- ortrans-1,4-cyclohexylene; and the like. Specifically, where T is1,4-phenylene, the poly(alkylene arylate) is a poly(alkyleneterephthalate). In addition, for poly(alkylene arylate), specificallyuseful alkylene groups D include, for example, ethylene, 1,4-butylene,and bis-(alkylene-disubstituted cyclohexane) including cis- and/ortrans-1,4-(cyclohexylene)dimethylene.

Examples of poly(alkylene terephthalates) include poly(ethyleneterephthalate) (PET), poly(1,4-butylene terephthalate) (PBT), andpoly(propylene terephthalate) (PPT). Also useful are poly(alkylenenaphthoates), such as poly(ethylene naphthanoate) (PEN), andpoly(butylene naphthanoate) (PBN). A specifically suitablepoly(cycloalkylene diester) is poly(cyclohexanedimethanol terephthalate)(PCT). Combinations comprising at least one of the foregoing polyestersmay also be used.

Copolymers comprising alkylene terephthalate repeating ester units withother suitable ester groups may also be useful. Specifically usefulester units may include different alkylene terephthalate units, whichcan be present in the polymer chain as individual units, or as blocks ofpoly(alkylene terphthalates). Specifically suitable examples of suchcopolymers include poly(cyclohexanedimethanolterephthalate)-co-poly(ethylene terephthalate), abbreviated as PETGwhere the polymer comprises greater than or equal to 50 mole % ofpoly(ethylene terephthalate), and abbreviated as PCTG where the polymercomprises greater than 50 mole % of poly(cyclohexanedimethanolterephthalate).

Suitable poly(cycloalkylene diester)s may include poly(alkylenecyclohexanedicarboxylate)s. Of these, a specific example ispoly(1,4-cyclohexane-dimethanol-1,4-cyclohexanedicarboxylate) (PCCD),having recurring units of formula (9):

wherein, as described using formula (8), D is a dimethylene cyclohexanegroup derived from cyclohexane dimethanol, and T is a cyclohexane ringderived from cyclohexanedicarboxylate or a chemical equivalent thereofand is selected from the cis- or trans-isomer or a mixture of cis- andtrans-isomers thereof.

The polycarbonate and polyester may be used in a weight ratio of 1:99 to99:1, specifically 10:90 to 90:10, and more specifically 30:70 to 70:30,depending on the function and properties desired.

It is desirable for such a polyester and polycarbonate blend to have amelt volume rate of about 5 to about 150 cc/10 min., specifically about7 to about 125 cc/10 min, more specifically about 9 to about 110 cc/10min, and still more specifically about 10 to about 100 cc/10 min.,measured at 300° C. and a load of 1.2 kilograms according to ASTMD1238-04. The above polyesters with a minor amount, e.g., from about 0.5to about 10 percent by weight, of units derived from an aliphatic diacidand/or an aliphatic polyol to make copolyesters.

The polycarbonate may also comprise a polysiloxane-polycarbonatecopolymer, also referred to as a polysiloxane-polycarbonate. Thepolysiloxane (also referred to herein as “polydiorganosiloxane”) blocksof the copolymer comprise repeating siloxane units (also referred toherein as “diorganosiloxane units”) of formula (10):

wherein each occurrence of R is same or different, and is a C₁₋₁₃monovalent organic radical. For example, R may independently be a C₁-C₁₃alkyl group, C₁-C₁₃ alkoxy group, C₂-C₁₃ alkenyl group, C₂-C₁₃alkenyloxy group, C₃-C₆ cycloalkyl group, C₃-C₆ cycloalkoxy group,C₆-C₁₄ aryl group, C₆-C₁₀ aryloxy group, C₇-C₁₃ arylalkyl group, C₇-C₁₃arylalkoxy group, C₇-C₁₃ alkylaryl group, or C₇-C₁₃ alkylaryloxy group.The foregoing groups may be fully or partially halogenated withfluorine, chlorine, bromine, or iodine, or a combination thereof.Combinations of the foregoing R groups may be used in the samecopolymer.

The value of D in formula (10) may vary widely depending on the type andrelative amount of each component in the thermoplastic composition, thedesired properties of the composition, and like considerations.Generally, D may have an average value of 2 to 1,000, specifically 2 to500, and more specifically 5 to 100. In one embodiment, D has an averagevalue of 10 to 75, and in still another embodiment, D has an averagevalue of 40 to 60. Where D is of a lower value, e.g., less than 40, itmay be desirable to use a relatively larger amount of thepolycarbonate-polysiloxane copolymer. Conversely, where D is of a highervalue, e.g., greater than 40, it may be necessary to use a relativelylower amount of the polycarbonate-polysiloxane copolymer.

A combination of a first and a second (or more)polysiloxane-polycarbonate copolymer may be used, wherein the averagevalue of D of the first copolymer is less than the average value of D ofthe second copolymer.

In one embodiment, the polydiorganosiloxane blocks are provided byrepeating structural units of formula (11):

wherein D is as defined above; each R may independently be the same ordifferent, and is as defined above; and each Ar may independently be thesame or different, and is a substituted or unsubstituted C₆-C₃₀ aryleneradical, wherein the bonds are directly connected to an aromatic moiety.Suitable Ar groups in formula (11) may be derived from a C₆-C₃₀dihydroxyarylene compound, for example a dihydroxyarylene compound offormula (3), (4), (6), or (7) above. Combinations comprising at leastone of the foregoing dihydroxyarylene compounds may also be used.Specific examples of suitable dihydroxyarylene compounds are1,1-bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane,2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane,2,2-bis(4-hydroxyphenyl)octane, 1,1-bis(4-hydroxyphenyl)propane,1,1-bis(4-hydroxyphenyl)n-butane,2,2-bis(4-hydroxy-1-methylphenyl)propane,1,1-bis(4-hydroxyphenyl)cyclohexane, bis(4-hydroxyphenyl sulphide), and1,1-bis(4-hydroxy-t-butylphenyl)propane. Combinations comprising atleast one of the foregoing dihydroxy compounds may also be used.

Units of formula (11) may be derived from the corresponding dihydroxycompound of formula (12):

wherein R, Ar, and D are as described above. Compounds of formula (12)may be obtained by the reaction of a dihydroxyarylene compound with, forexample, an alpha, omega-bisacetoxypolydiorangonosiloxane under phasetransfer conditions.

In another embodiment, polydiorganosiloxane blocks comprise units offormula (13):

wherein R and D are as described above, and each occurrence of R¹ isindependently a divalent C₁-C₃₀ alkylene, and wherein the polymerizedpolysiloxane unit is the reaction residue of its corresponding dihydroxycompound. In a specific embodiment, the polydiorganosiloxane blocks areprovided by repeating structural units of formula (14):

wherein R and D are as defined above. Each R² in formula (14) isindependently a divalent C₂-C₈ aliphatic group. Each M in formula (14)may be the same or different, and may be a halogen, cyano, nitro, C₁-C₈alkylthio, C₁-C₈ alkyl, C₁-C₈ alkoxy, C₂-C₈ alkenyl, C₂-C₈ alkenyloxygroup, C₃-C₈ cycloalkyl, C₃-C₈ cycloalkoxy, C₆-C₁₀ aryl, C₆-C₁₀ aryloxy,C₇-C₁₂ arylalkyl, C₇-C₁₂ arylalkoxy, C₇-C₁₂ alkylaryl, or C₇-C₁₂alkylaryloxy, wherein each n is independently 0, 1, 2, 3, or 4.

In one embodiment, M is bromo or chloro, an alkyl group such as methyl,ethyl, or propyl, an alkoxy group such as methoxy, ethoxy, or propoxy,or an aryl group such as phenyl, chlorophenyl, or tolyl; R² is adimethylene, trimethylene or tetramethylene group; and R is a C₁₋₈alkyl, haloalkyl such as trifluoropropyl, cyanoalkyl, or aryl such asphenyl, chlorophenyl or tolyl. In another embodiment, R is methyl, or amixture of methyl and trifluoropropyl, or a mixture of methyl andphenyl. In still another embodiment, M is methoxy, n is one, R² is adivalent C₁-C₃ aliphatic group, and R is methyl.

Units of formula (14) may be derived from the corresponding dihydroxypolydiorganosiloxane (15):

wherein R, D, M, R², and n are as described above. Such dihydroxypolysiloxanes can be made by effecting a platinum catalyzed additionbetween a siloxane hydride of formula (16):

wherein R and D are as previously defined, and an aliphaticallyunsaturated monohydric phenol. Suitable aliphatically unsaturatedmonohydric phenols included, for example, eugenol, 2-allylphenol,4-allyl-2-methylphenol, 4-allyl-2-phenylphenol, 4-allyl-2-bromophenol,4-allyl-2-t-butoxyphenol, 4-phenyl-2-phenylphenol,2-methyl-4-propylphenol, 2-allyl-4,6-dimethylphenol,2-allyl-4-bromo-6-methylphenol, 2-allyl-6-methoxy-4-methylphenol and2-allyl-4,6-dimethylphenol. Mixtures comprising at least one of theforegoing may also be used.

The polysiloxane-polycarbonate may comprise 50 to 99 wt % of carbonateunits and 1 to 50 wt % siloxane units. Within this range, thepolysiloxane-polycarbonate copolymer may comprise 70 to 98 wt %,specifically 75 to 97 wt % of carbonate units and 2 to 30 wt %,specifically 3 to 25 wt % siloxane units.

In an embodiment, the polysiloxane-polycarbonate may comprisepolysiloxane units, and carbonate units derived from bisphenol A, e.g.,the dihydroxy compound of formula (3) in which each of A¹ and A² isp-phenylene and Y¹ is isopropylidene. Polysiloxane-polycarbonates mayhave a weight average molecular weight of 2,000 to 100,000, specifically5,000 to 50,000 as measured by gel permeation chromatography using acrosslinked styrene-divinyl benzene column, at a sample concentration of1 milligram per milliliter, and as calibrated with polycarbonatestandards.

The polysiloxane-polycarbonate can have a melt volume flow rate,measured at 300° C./1.2 kg, of 1 to 50 cubic centimeters per 10 minutes(cc/10 min), specifically 2 to 30 cc/10 min. Mixtures ofpolysiloxane-polycarbonates of different flow properties may be used toachieve the overall desired flow property.

The thermoplastic composition comprises a sulfonate end-cappedpolycarbonate of formula (17):Z-S(O)₂—O-(-L-)_(m)-O—S(O)₂-Z  (17)wherein each Z is independently an alkyl or aryl group. Suitable groupsinclude C₁-C₂₀ alkyl group, substituted C₁-C₂₀ alkyl group, C₆-C₂₀ arylgroup, or substituted C₆-C₂₀ aryl group. When present, substituents onthe Z groups may include, for example, nitro, cyano, hydroxy, thio,halogen (fluoro, chloro, bromo, iodo), C₁-C₈ alkyl, C₁-C₈ alkyl ether,C₁-C₈ acyl, C₆-C₂₀ aryl, or C₆-C₂₀ aryloxy. Examples of suitable Zgroups include methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl,n-pentyl, isopentyl, n-hexyl, n-octyl, 2-ethylhexyl, cyclohexyl,4-ethylcyclohexyl, 4-ethylcyclohexyl-2-ethyl, n-dodecyl, n-octadecyl,camphoryl, adamantyl, norbornyl, trifluoromethyl, 2,2,2-trifluoroethyl,perfluoro-n-butyl, perfluorocyclohexyl, phenyl, 2-methylphenyl,3-methylphenyl, 4-methylphenyl, 3,5-dimethylphenyl, 2,3-dimethylphenyl,2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl,2,3,4-trimethylphenyl, 2,3,5-trimethylphenyl, 3,4,5-trimethylphenyl,2,4,6-trimethylphenyl, 4-ethyl phenyl, 4-butyl phenyl,4-tert-butyl-phenyl, 2-trifluoromethylphenyl, 4-trifluoromethylphenyl,4-methoxyphenyl, 4-tert-butoxyphenyl, 4-acetylphenyl, 4-fluorophenyl,4-chlorophenyl, 4-bromophenyl, naphthyl, C₁-C₈ alkyl-substitutednaphthyl, C₁-C₈ alkyl ether-substituted naphthyl, halogen-substitutednaphthyl, and the like.

Also in formula (17), -(-L-)_(m)- is a polycarbonate linking groupcomprising m units of linking unit L, wherein m is at least one. In anembodiment, m is 1 to 500. Suitable L units include carbonate units offormula (1), ester units of formula (8), poly(arylene ether) units, softblock units, or a combination comprising at least one of these. In anembodiment, at least one L is a carbonate unit. In a further embodiment,in addition to the carbonate unit, L may include poly(arylene ether)units of formula (18):—(—Ar¹—X—Ar¹—O—)_(n)—Ar¹—X—Ar¹—  (18)wherein n is 0 to 200, and wherein each Ar¹ is independently asubstituted or unsubstituted C₆-C₂₀ arylene group. When present,substituents on the Ar¹ groups may include, for example, nitro, cyano,hydroxy, thio, halogen (fluoro, chloro, bromo, iodo), C₁-C₈ alkyl, C₁-C₈acyl, or C₁-C₈ alkyl ether. Examples of suitable arylene groups include1,2-phenylene, 1,3-phenylene, 1,4-phenylene, 2-methyl-1,4-phenylene,5-methyl-1,3-phenylene, 2-methoxy-1,4-phenylene,2,5-dimethyl-1,4-phenylene, 2,6-dimethyl-1,4-phenylene,2,3,5,6-tetramethyl-1,4-phenylene, 1,4-naphthalenediyl,1,5-naphthalenediyl, 2,6-naphthalenediyl, and the like.

Also in formula (18), X is a bridging radical having one or two atomsthat separate the Ar¹ groups. In an exemplary embodiment, one atomseparates the Ar¹ groups. Illustrative non-limiting examples of radicalsof this type are —O—, —S—, —S(O)—, —S(O₂)—, —C(O)—, methylene,cyclohexyl-methylene, 2-[2.2.1]-bicycloheptylidene, ethylidene,isopropylidene, neopentylidene, isatinylene, spirobiindanylene,phthalimidine, cyclohexylidene, cyclopentadecylidene, cyclododecylidene,and adamantylidene.

Poly(arylene ether) groups of formula (18) may be derived from thecorresponding dihydroxy compound of formula (19):HO—(—Ar¹—X—Ar¹—O—)_(n)—Ar¹—X—Ar¹—OH   (19)wherein Ar¹, X, and n are as described above. Examples of suitabledihydroxy poly(arylene ether) compounds include, but are not limited to,polyalkylene-arylene ethers such as poly(bisphenol-A ether);poly(arylene ether) sulfones such as poly(diphenylether)sulfone;poly(arylene ether) sulfides such as poly(diphenylene ether) sulfide;and the like, and a combination comprising at least one of these.

In another further embodiment, in addition to the carbonate and/or esterunits, L may comprise a soft-block unit. As used herein, the term “softblock” is used to describe an oligomeric or polymeric unit having a Tglower than that of the polycarbonate and/or polyester units with whichit forms a copolymer. Soft blocks comprising soft block units, whereused, desirably have thermal stability to melt processing attemperatures of at least 240° C. Soft block units, when copolymerizedwith carbonate units, ester units, or a combination comprising at leastone of these, may form a copolymer having alternating, random, or blockarrangements of the soft block unit. Suitable soft block units includepolysiloxane units, polyalkylene oxide units, poly(alkylene ester)units, polyolefin units, or a combination comprising at least one ofthese.

Where linking group L comprises a soft block unit, the soft block unitmay be derived from an oligomeric or polymeric dihydroxy compound havingthe general formula HO-G-OH, where G is the soft block unit. Examples ofsuitable oligomeric or polymeric dihydroxy compounds from which the softblock units are derived include, but are not limited to,dihydroxy-capped polydiorganosiloxanes of formulas (12) and (15);dihydroxy poly(alkylene oxide)s such as polyethylene glycol,polypropylene glycol, poly(ethylene glycol)-co-(propylene glycol), andthe like; hydroxy end-capped poly(alkylene ester)s such as poly(ethyleneterephthalate), poly(1,4-butylene terephthalate), poly(1,4-dimethylenecyclohexane terephthalate), poly(1,4-dimethylene cyclohexane-bis1,4-cyclohexanedicarboxylate), poly(ethyleneterephthalate)-co-(1,4-dimethylene cyclohexane terephthalate), and thelike; polyolefins such as dihydroxy derivatives of polyethylene,polypropylene, poly(ethylene-co-propylene), and the like; and acombination comprising at least one of the foregoing. Specificallyuseful examples of suitable dihydroxy compounds include bisphenol-A,dihydroxy-capped poly(isophthalate-terephthalate resorcinol) esters,dihydroxy-capped poly(isophthalate-terephthalate bisphenol-A) esters,eugenol-capped polydimethylsiloxane, bisphenol-A cappedpolydimethylsiloxane, dihydroxy-capped poly(bisphenol-A) ether, ethyleneglycol-capped poly(ethylene terephthalate), poly(ethylene glycol), andthe like, or a combination comprising at least one of the foregoing.

A polyarylene block or soft block, where used, may be present along withthe carbonate and/or ester units in a weight ratio of 50:50 to 1:99,specifically 40:60 to 2:98, and still more specifically 30:70 to 3:97.

Thus, in an embodiment, suitable sulfonate end-capped polycarbonates offormula (17) include sulfonate end-capped polycarbonate homopolymers,sulfonate end-capped polycarbonate copolymers, sulfonate end-cappedpolyester-polycarbonate, sulfonate end-cappedpolysiloxane-polycarbonate, sulfonate end-cappedpolysiloxane-co-(polyester-polycarbonate), sulfonate end-cappedpoly(arylene ether)-co-polycarbonate, sulfonate end-capped poly(aryleneether)-co-(polyester-polycarbonate), sulfonate end-capped poly(alkyleneester)-co-polycarbonate, sulfonate end-capped poly(alkyleneester)-co-(polyester-polycarbonate), sulfonate end-capped poly(alkyleneether)-co-polycarbonate, sulfonate end-capped poly(alkyleneether)-co-(polyester-polycarbonate), sulfonate end-cappedpolyolefin-co-polycarbonate, sulfonate end-cappedpoly(olefin)-co-(polyester-polycarbonate), or a combination comprisingat least one of these. In an exemplary embodiment, a sulfonateend-capped polycarbonate is a tosyl end-capped poly(bisphenol-Acarbonate).

Sulfonate end-capped polycarbonates of formula (17) may be derived fromthe condensation reaction of a dihydroxy compound, a reactive derivativeof a sulfonic acid, and a reactive carbonyl compound, such as forexample phosgene, a dialkly- or diarylchloroformate, a phosgenederivative, such as, diphosgene or triphosgene, or the like. Thesulfonate end-capped polycarbonate may generally be prepared by aqueousbiphasic reaction similar to that described hereinabove for thepreparation of polycarbonates, polyesters, and polyester-polycarbonates.Specifically, in the method of preparing the sulfonate end-cappedpolycarbonates herein, the reactive sulfonic acid derivative is includedas a chain stopper.

Suitable dihydroxy compounds from which the sulfonate end-cappedpolycarbonate may be derived include those having the formula HO—R¹—OH,including dihydroxy aromatic compounds of formulas (3), (4), (6), (7),and examples described therein; dihydroxy poly(arylene ether)s offormula (19), as described above; and dihydroxy soft blocks of generalformula HO-G-OH, also as described above, and a combination comprisingat least one of these.

In an embodiment, derivatives of sulfonic acids may be used as chainstoppers. Suitable derivatives of sulfonic acids may include, forexample, sulfonic acid halides including acid chlorides and fluorides;anhydrides; and mixed anhydrides. Sulfonic acid chlorides arespecifically useful. Suitable reactive sulfonic acid derivatives includethose derived from C₁-C₂₂ alkyl sulfonic acids, substituted C₁-C₂₂ alkylsulfonic acids, C₁-C₂₂ cycloalkyl sulfonic acids, substituted C₁-C₂₂cycloalkyl sulfonic acids, C₆-C₃₀ aryl sulfonic acids, substitutedC₆-C₃₀ aryl sulfonic acids, C₆-C₃₀ arylalkyl sulfonic acids, andsubstituted C₆-C₃₀ arylalkyl sulfonic acids. Substituents where used mayinclude, for example, nitro, cyano, hydroxy, thio, halogen (fluoro,chloro, bromo, iodo), C₁-C₈ alkyl, C₁-C₈ acyl, or C₁-C₈ alkyl ether.Examples of reactive sulfonic acid derivatives that may be used include,but are not limited to, methanesulfonyl chloride (mesyl chloride),ethanesulfonyl chloride, n-butanesulfonyl chloride, n-hexanesulfonylchloride, n-octanesulfonyl chloride, n-dodecanesulfonyl chloride,n-octadecylsulfonyl chloride, cyclohexanesulfonyl chloride,4-ethylcyclohexane sulfonyl chloride, (4-ethylcyclohexyl)ethane sulfonylchloride, camphorsulfonyl chloride, trifluoromethanesulfonyl chloride,perfluoroethane sulfonyl chloride, perfluoro-n-butanesulfonyl fluoride,perfluoro-n-butane sulfonyl chloride, perfluorocyclohexane sulfonylfluoride, perfluorocyclohexane sulfonyl chloride,2,2,2-trifluoroethylsulfonyl chloridebenzenesulfonyl chloride,2-methylbenzenesulfonyl chloride, 3-methylbenzenesulfonyl chloride,4-methylbenzenesulfonyl chloride (also referred to as toluenesulfonylchloride, and as tosyl chloride), 3,5-dimethylbenzenesulfonyl chloride,2,3-dimethylbenzenesulfonyl chloride, 2,4-dimethylbenzenesulfonylchloride, 2,5-dimethylbenzenesulfonyl chloride,2,6-dimethylbenzenesulfonyl chloride, 2,3,4-trimethylbenzenesulfonylchloride, 2,3,5-trimethylbenzenesulfonyl chloride,3,4,5-trimethylbenzenesulfonyl chloride, 2,4,6-trimethylbenzenesulfonylchloride, 4-ethyl benzenesulfonyl chloride, 4-n-butyl benzenesulfonylchloride, 4-tert-butylbenzenesulfonyl chloride, 4-methoxybenzenesulfonylchloride, 4-tert-butoxybenzenesulfonyl chloride, 2-fluorobenzenesulfonylchloride, 4-fluorobenzenesulfonyl chloride, 4-chlorobenzenesulfonylchloride, 4-bromobenzenesulfonyl chloride, 4-acetylbenzenesulfonylchloride, 2-trifluoromethylbenzenesulfonyl chloride,3-trifluoromethylbenzenesulfonyl chloride,4-trifluoromethylbenzenesulfonyl chloride, naphthalenesulfonyl chloride,C₁₋₈ alkyl naphthalenesulfonyl chlorides, C₁₋₈ alkyloxynaphthalenesulfonyl chlorides, halo-substituted naphthalenesulfonylchlorides, and the like. Of the derivatives of the foregoing,toluenesulfonyl chloride (also referred to as tosyl chloride) isspecifically useful. The reactive sulfonic acid derivative chainstoppers may be used alone or as a combination comprising at least oneof the foregoing reactive sulfonic acid derivative chain stoppers.Alternatively, the reactive sulfonic acid derivative chain stoppers maybe used in combination with at least one of the aforementionedmono-phenolic compounds, mono-carboxylic acid chlorides, and/ormono-chloroformates.

The condensation reaction between the reactive sulfonic acid derivativeand dihydroxy compounds to form the sulfonate end-capped polycarbonatesof formula (17) may generally be carried out in a single phase using anorganic solvent, in the presence of a base. Alternatively, thecondensation reaction may be carried out in a biphasic reaction using anorganic solvent and water, in the presence of a base.

In an embodiment, suitable methods for forming a sulfonate end-cappedpolycarbonate are disclosed. In one method, for example, a dihydroxycompound, reactive sulfonic acid derivative, a base, solvent, andactivated carbonyl compound are combined in a medium, wherein the pH ofthe medium is maintained at about 9 to about 11 while combining andreacting, and is biphasic, having an organic phase and an aqueous phase.Suitable bases include, for example, triethylamine, sodium hydroxide,sodium carbonate, sodium bicarbonate, sodium acetate, sodium gluconate,sodium citrate, sodium tartrate, and the like, or a combinationcomprising at least one of these. Maintaining pH may also be done byaddition of a suitable base, for example sodium hydroxide, as neededduring the reaction. In an embodiment, the activated carbonyl compoundis phosgene, a phosgene derivative, dichloroformate, or a combinationcomprising at least one of these. In another method, for example, aphase transfer catalyst having the formula (R³)₄Q⁺X, wherein R³, Q, andX are as defined above, may be included. An example of a specificallyuseful phase transfer catalyst is methyl tri-n-butyl ammonium chloride.In another method, for example, a suitable dihydroxy compound comprisesa dihydroxy aromatic compound, a dihydroxy poly(arylene ether), adihydroxy soft-block compound, or a combination comprising at least oneof the foregoing. In an embodiment, where a combination is used, thedihydroxy poly(arylene ether) or dihydroxy soft block is used todisplace a portion of the dihydroxy aromatic compound charge. In anotherfurther method, for example, the mono-haloformate, bis-haloformate, or acombination comprising mono- and bis-haloformates of the dihydroxypolyarylene or dihydroxy soft-block compounds are used. The resultingsulfonate end-capped polycarbonate may be isolated by precipitation fromthe medium by addition to a non-solvent. Proportions, types, and amountsof the reaction ingredients may be determined and selected by oneskilled in the art to provide sulfonate end-capped polycarbonates havingdesirable physical properties including but not limited to, for example,suitable molecular weight, MVR, and glass transition temperature. In anexample of a specific embodiment, the dihydroxy compound used isbisphenol-A. In another example of a specific embodiment, a suitablereactive sulfonic acid derivative is p-toluenesulfonyl chloride (tosylchloride). In another example of a specific embodiment, a sulfonateend-capped polycarbonate made by the above method is a tosyl end-cappedpoly(bisphenol-A carbonate). In an embodiment, the glass transitiontemperature of a sulfonate end-capped polycarbonate is comparable tothat of a similar polycarbonate polymer of the same composition butwithout sulfonate end groups. In an exemplary embodiment, tosylend-capped poly(bisphenol-A carbonate) prepared by the above method hasa Tg of 145-150° C., comparable to that of a similar poly(bisphenol-Acarbonate) prepared without tosyl end groups.

Biphasic condensation of reactive sulfonic acid derivatives, includingsulfonic acid chlorides, may result in an inefficient interfacialreaction between the dihydroxy compound and the sulfonic acid chloride.An inefficient condensation between these may lead to both increasedhydrolysis of the sulfonic acid chloride to the non-reacting sulfonicacid, and an uncontrolled, higher molecular weight polymer due to theinefficient reaction of dihydroxy species and the sulfonic acidchloride. In an advantageous feature of the above-described method ofpreparing the sulfonate end-capped polycarbonate, it has been found thatcarrying out the condensation in the presence of a suitable phasetransfer catalyst provides a more efficient condensation of the reactivesulfonic acid derivative with the dihydroxy compound. It is believedthat the phase transfer catalyst increases the reacting concentration ofthe dihydroxy species in the organic phase, thus providing a morecomplete condensation of the dihydroxy compound and reactive sulfonicacid derivative.

While it is not required to provide an explanation of how an inventionworks, such theories may be useful for the purposes of better helpingthe reader to comprehend the invention. It is to be understood thereforethat the claims are not to be limited by the following theory ofoperation. Thus, without wishing to be bound by theory, where no phasetransfer catalyst is used, condensation of phosgene and the dihydroxyspecies can proceed rapidly relative to the condensation of the reactivesulfonic acid derivative and the dihydroxy compound, which may generateearly polymerized species having a high averaged molecular weight forthe oligomeric chains. As rapid polymerization proceeds, thedistribution of molecular weights of the chains may further increase asoligomers of different lengths randomly condense to form polymers ofdiffering chain length. Rapid growth in oligomeric dihydroxy speciescondensing with phosgene, and without a similar kinetically controlledstatistical condensing of the oligomeric dihydroxy species with thereactive sulfonic acid derivative, may therefore result in widedistribution of weight averaged molecular weight to number averagedmolecular weight (Mw/Mn), i.e., polydispersity, and a higher thanexpected, uncontrolled molecular weight. A higher polydispersity may beless desirable in a polymer as it may adversely affect one or morephysical and/or mechanical properties of the polymer such as forexample, but not limited to, glass transition temperature, melt-volumerate (MVR), impact strength. Use of a phase transfer catalyst in themethod has been found to provide a lower rate of phosgenation that iscomparable with the rate of reaction of the reactive sulfonic acidderivative, and thus may provide a sulfonate end-capped polycarbonatehaving a more consistent molecular weight and lower polydispersity(Mw/Mn of less than 2.4). In addition, lower amounts of residualreactive sulfonic acid derivative are present than would be obtained inthe absence of a phase transfer catalyst. In a specific embodiment, theconcentration of residual reactive sulfonic acid derivative in thesulfonate end-capped polycarbonate is less than or equal to 5%,specifically less than 2.5%, and more specifically less than 1% based onthe total weight of the sulfonate end-capped polycarbonate.

The sulfonate end-capped polycarbonate is used in the thermoplasticcomposition in an amount effective to inhibit yellowing of thepolycarbonate upon irradiation, in particular exposure to gammaradiation. Effective amounts are readily determined by one of ordinaryskill in the art, and will vary depending upon the type of resin(s) usedin the composition, the type and amount of other additives, and theintended use of the composition. The sulfonate end-capped polycarbonatesare generally completely miscible with polycarbonates, and possessequivalent physical and rheological properties to comparablecompositions without sulfonate end groups.

An amount of sulfonate end-capped polycarbonate useful for improvingionizing radiation stability may be determined according to the molarquantity of the sulfonate end-group present in the thermoplasticcomposition. This amount can correlate to the amount of reactivesulfonic acid derivative initially used to prepare the sulfonateend-capped polycarbonate. The amount of sulfonate end-group may bedetermined after isolation of the polymer for the sulfonate end-cappedpolycarbonate, by using end group analysis methods such as, for example,proton nuclear magnetic resonance spectrometry (¹H NMR), and/or bycalculating the number of end groups from the number-averaged molecularweight Mn (as determined using a suitable molecular weight determinationmethod including, but not limited to gel permeation chromatography(GPC), dynamic light scattering, vapor phase osmometry, or othersuitable methods). As disclosed herein, the sulfonate end-cappedpolycarbonate has a number averaged molecular weight (Mn) of 1,000 to100,000, specifically 2,000 to 75,000, more specifically 5,000 to50,000, and still more specifically 7,500 to 25,000, as determined byGPC using a crosslinked styrene-divinylbenzene column calibrated usingpolycarbonate standards, and a sample concentration of 1 milligram permilliliter (mg/ml). The sulfonate end-capped polycarbonate may also havea weight averaged molecular weight (Mw) of 2,000 to 200,000,specifically 3,000 to 150,000, more specifically 5,000 to 100,000, andstill more specifically 7,500 to 50,000, as determined by GPC using acrosslinked styrene-divinylbenzene column calibrated using polycarbonatestandards, and a sample concentration of 1 mg/ml.

In general, sulfonate end groups are present in the sulfonate end-cappedpolycarbonate an amount of 0.01 to 10 mole-percent (mol %), morespecifically 0.1 to 8 mol %, even more specifically 1 to 7.5 mol %, andeven more specifically 2 to 7 mol % per the total number of moles ofrepeating unit L present in the sulfonate end-capped polycarbonate.Amounts lower than 0.01 mol % of sulfonate end groups may not beeffective, while amounts greater than about 10 mol % of sulfonate endgroups may not lead to improved stability, and/or may adversely affectone or more physical and/or mechanical properties of the thermoplasticcomposition.

In general, an effective molar equivalent amount of sulfonate end groupas provided by the sulfonate end-capped polycarbonate is present in thethermoplastic composition in an amount of 0.001 to 500 millimoles perkilogram (mmol/Kg), specifically 0.01 to 50 mmol/Kg, and morespecifically 0.1 to 5 mmol/Kg of the total weight of the thermoplasticcomposition. Amounts lower than 0.001 mmol/Kg may not be effective,while amounts greater than about 500 mmol/Kg do not lead to improvedstability, and/or can adversely affect one or more physical and/ormechanical properties of the thermoplastic composition. In anembodiment, a masterbatch composition comprising polycarbonate andlevels of 5 to 500 mmol/Kg of sulfonate end-capped polycarbonate may beprepared, wherein the masterbatch is further combined with polycarbonateand/or other polymer to form the thermoplastic composition.

In an unexpected and advantageous feature, however, it has been foundthat sulfonate end-capped polycarbonate, used alone or as a combinationwith other polymers, is effective to prevent yellowing upon exposure toradiation, including gamma radiation. In an embodiment, the sulfonateend-capped polycarbonate is used in an amount of 0.1 to 100 wt %,specifically 1 to 80 wt %, more specifically 2 to 50 wt %, still morespecifically 5 to 40 wt %, and still more specifically 9 to 30 wt %,based on the total weight of the thermoplastic composition, with theproviso that the amount and type of sulfonate end-capped polycarbonateused is selected so that the overall concentration of sulfonate endgroups is not greater than a molar concentration of 500 millimoles perkilogram (mmol/Kg), and is not less than 0.001 mmol/Kg, of the totalweight of the thermoplastic composition.

The thermoplastic composition may further comprise an ionizing radiationstabilizing additive. Exemplary ionizing radiation stabilizing additivesinclude certain aliphatic alcohols, aromatic alcohols, aliphatic diols,aliphatic ethers, esters, diketones, alkenes, thiols, thioethers andcyclic thioethers, sulfones, dihydroaromatics, diethers, nitrogencompounds, or a combination comprising at least one of the foregoing.Alcohol-based stabilizing additives may be selected from mono, di-, orpolysubstituted alcohols, and can be straight, branched, cyclic and/oraromatic. Suitable aliphatic alcohols may include alkenols with sites ofunsaturation, examples of which include 4-methyl-4-penten-2-ol,3-methyl-pentene-3-ol, 2-methyl-4-penten-2-ol,2,4-dimethyl-4-penten-2-ol, 2-phenyl-4-penten-2-ol, and 9-decen-1-ol;tertiary alcohols including 3-hydroxy-3-methyl-2-butanone,2-phenyl-2-butanol, and the like; hydroxy-substituted tertiarycycloaliphatics such as 1-hydroxy-1-methyl-cyclohexane; andhydroxymethyl aromatics having an aromatic ring with carbinolsubstituents such as a methylol group (—CH₂OH) or a more complexhydrocarbon group such as (—CRHOH) or (—CR₂OH), wherein R is straightchain C₁-C₂₀ alkyl or branched C₁-C₂₀ alkyl. Exemplary hydroxy carbinolaromatics include benzhydrol, 2-phenyl-2-butanol, 1,3-benzenedimethanol,benzyl alcohol, 4-benzyloxy-benzyl alcohol, and benzyl-benzyl alcohol.

Useful classes of ionizing radiation stabilizing additives are di- andpolyfunctional aliphatic alcohols, also referred to as aliphatic diolsand aliphatic polyols. Specifically useful are aliphatic diols offormula (20):HO—(C(A′)(A″))_(d)-S—(C(B′)(B″))_(e)—OH  (20)wherein A′, A″, B′, and B″ are each independently H or C₁-C₆ alkyl; S isC₁-C₂₀ alkyl, C₂-C₂₀ alkyleneoxy, C₃-C₆ cycloalkyl, or C₃-C₆ substitutedcycloalkyl; and d and e are each 0 or 1, with the proviso that, when dand e are each 0, S is selected such that both —OH groups are notconnected directly to a single common carbon atom.

In formula (20), A′, A″, B′, and B″ can each be independently selectedfrom H, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl,n-pentyl, 2-pentyl, 3-pentyl, isopentyl, neopentyl, n-hexyl, 2-hexyl,3-hexyl, 2-methyl pentyl, 3-methylpentyl, 2,2-dimethylbutyl,2,3-dimethylbutyl, and the like, and a combination comprising at leastone of the foregoing alkyl groups.

Spacer group S can be selected from methanediyl, ethanediyl,1,1-ethanediyl, 1,1-propanediyl, 1,2-propanediyl, 1,3-propanediyl,2,2-propanediyl, 1,1-butanediyl, 1,2-butanediyl, 1,3-butanediyl,1,4-butanediyl, 2,2-butanediyl, 2,3-butanediyl, 1,1-pentanediyl,1,2-pentanediyl, 1,3-pentanediyl, 1,4-pentanediyl, 1,5-pentanediyl,2,2-pentanediyl, 2,3-pentanediyl, 2,4-pentanediyl, 3,3-pentanediyl,2-methyl-1,1-butanediyl, 3-methyl-1,1-butanediyl,2-methyl-1,2-butanediyl, 2-methyl-1,3-butanediyl,2-methyl-1,4-butanediyl, 2-methyl-2,2-butanediyl,2-methyl-2,3-butanediyl, 2,2-dimethyl-1,1-propanediyl,2,2-dimethyl-1,2-propanediyl, 2,2-dimethyl-1,3-propanediyl,3,3-dimethyl-1,1-propanediyl, 3,3-dimethyl-1,2-propanediyl,3,3-dimethyl-2,2-propanediyl, 1,1-dimethyl-2,3-propanediyl,3,3-dimethyl-2,2-propanediyl, 1,1-hexanediyl, 1,2-hexanediyl,1,3-hexanediyl, 1,4-hexanediyl, 1,5-hexanediyl, 1,6-hexanediyl,2,2-hexanediyl, 2,3-hexanediyl, 2,4-hexanediyl, 2,5-hexanediyl,3,3-hexanediyl, 2-methyl-1,1-pentanediyl, 3-methyl-1,1-pentanediyl,2-methyl-1,2-pentanediyl, 2-methyl-1,3-pentanediyl,2-methyl-1,4-pentanediyl, 2-methyl-2,2-pentanediyl,2-methyl-2,3-pentanediyl, 2-methyl-2,4-pentanediyl,2,2-dimethyl-1,1-butanediyl, 2,2-dimethyl-1,2-butanediyl,2,2-dimethyl-1,3-butanediyl, 3,3-dimethyl-1,1-butanediyl,3,3-dimethyl-1,2-butanediyl, 3,3-dimethyl-2,2-butanediyl,1,1-dimethyl-2,3-butanediyl, 3,3-dimethyl-2,2-butanediyl, and the like;isomers of octanediyl, decanediyl, undecanediyl, dodecanediyl,hexadecanediyl, octadecanediyl, icosananediyl, and docosananediyl; andsubstituted and unsubstituted cyclopropanediyl, cyclobutanediyl,cyclopentanediyl, cyclohexanediyl, wherein substituents may be thepoints of radical attachment, such as in 1,4-dimethylenecyclohexane, ormay include branched and straight chain alkyl, cycloalkyl, and the like.Additionally, the spacer group S may be selected from one or morediradicals comprising polyalkyleneoxy units, such as ethyleneoxy,1,2-propyleneoxy, 1,3-propyleneoxy, 1,2-butyleneoxy, 1,4-butyleneoxy,1,6-hexyleneoxy, and the like; and a combination comprising at least oneof these.

Specific examples of suitable aliphatic diols include ethylene glycol,propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol,meso-2,3-butanediol, 1,2-pentanediol, 2,3-pentanediol, 1,4-pentanediol,1,4-hexandiol, and the like; alicyclic alcohols such as1,3-cyclobutanediol, 2,2,4,4-tetramethylcyclobutanediol,1,2-cyclopentanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol,1,4-cyclohexanediol, 1,4-dimethylolcyclohexane, and the like; branchedacyclic diols such as 2,3-dimethyl-2,3-butanediol (pinacol), and2-methyl-2,4-pentanediol (hexylene glycol); andpolyalkyleneoxy-containing alcohols such as polyethylene glycol,polypropylene glycol, block or randompoly(ethyleneglycol-co-propyleneglycols), and diols of copolymerscontaining polyalkyleneoxy-groups. Useful polyols may includepolyaryleneoxy compounds such as polyhydroxystyrene; alkyl polyols suchas polyvinylalcohol, polysaccharaides, and esterified polysaccharides. Acombination comprising at least one of the foregoing may also be useful.Specifically suitable diols include 2-methyl-2,4-pentanediol (hexyleneglycol), polyethylene glycol, and polypropylene glycol.

Suitable aliphatic ethers may include alkoxy-substituted cyclic oracyclic alkanes such as, for example, 1,2-dialkoxyethanes,1,2-dialkoxypropanes, 1,3-dialkoxypropanes, alkoxycyclopentanes,alkoxycyclohexanes, and the like. Ester compounds (—COOR) may be usefulas stabilizers wherein R may be a substituted or unsubstituted, aromaticor aliphatic, hydrocarbon and the parent carboxy compound may likewisebe substituted or unsubstituted, aromatic or aliphatic, and/or mono- orpolyfunctional. When present, substituents may include, for example,C₁-C₈ alkyl, C₁-C₈ alkyl ether, C₆-C₂₀ aryl, and the like. Esters whichhave proven useful includetetrakis(methylene[3,5-di-t-butyl-4-hydroxy-hydrocinnamate])methane,2,2′-oxamido bis(ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, andtrifunctional hindered phenolic ester compounds such as GOOD-RITE® 3125,available from B.F. Goodrich in Cleveland Ohio.

Diketone compounds may also be used, specifically those having twocarbonyl functional groups and separated by a single intervening carbonatoms such as, for example 2,4-pentadione.

Sulfur-containing compounds, suitable for use as stabilizing additives,can include thiols, thioethers and cyclic thioethers. Thiols include,for example, 2-mercaptobenzothiazole; thioethers includedilaurylthiopropionate; and cyclic thioethers include 1,4-dithiane,1,4,8,11-tetrathiocyclotetradecane. Cyclic thioethers containing morethan one thioether group are useful, specifically those having a singleintervening carbon between two thioether groups such as in, for example,1,3-dithiane. The cyclic ring may contain oxygen or nitrogen members.

Aryl or alkyl sulfone stabilizing additives of general structureR—S(O)₂—R′ may also be used, where R and R′ comprise C₁-C₂₀ alkyl,C₆-C₂₀ aryl, C₁-C₂₀ alkoxy, C₆-C₂₀ aryloxy, substituted derivativesthereof, and the like, and wherein at least one of R or R′ is asubstituted or unsubstituted benzyl. When present, substituents mayinclude, for example, C₁-C₈ alkyl, C₁-C₈ alkyl ether, C₆-C₂₀ aryl, andthe like. An example of a specifically useful sulfone is benzylsulfone.

Alkenes may be used as stabilizing additives. Suitable alkenes mayinclude olefins of general structure RR′C═CR″R′″ wherein R, R′, R″, andR′″ may each individually be the same or different and may be selectedfrom hydrogen, C₁-C₂₀ alkyl, C₁-C₂₀ cycloalkyl, C₁-C₂₀ alkenyl, C₁-C₂₀cycloalkenyl, C₆-C₂₀ aryl, C₆-C₂₀ arylalkyl, C₆-C₂₀ alkylaryl, C₁-C₂₀alkoxy, C₆-C₂₀ aryloxy and substituted derivatives thereof. Whenpresent, substituents may include, for example, C₁-C₈ alkyl, C₁-C₈ alkylether, C₆-C₂₀ aryl, and the like. The olefins may be acyclic, exocyclic,or endocyclic. Examples of specifically useful alkenes include1,2-diphenyl ethane, allyl phenol, 2,4-dimethyl-1-pentene, limonene,2-phenyl-2-pentene, 2,4-dimethyl-1-pentene, 1,4-diphenyl-1,3-butadiene,2-methyl-1-undecene, 1-dodecene, and the like, or a combinationcomprising at least one of the foregoing.

Hydroaromatic compounds may also be useful as stabilizing additives,including partially hydrogenated aromatics, and aromatics in combinationwith an unsaturated ring. Specific aromatics include benzene and/ornaphthalene based systems. Examples of suitable hydroaromatic compoundsinclude indane, 5,6,7,8-tetrahydro-1-naphthol,5,6,7,8-tetrahydro-2-naphthol, 9,10-dihydro anthracene,9,10-dihydrophenanthrene, 1-phenyl-1-cyclohexane,1,2,3,4-tetrahydro-1-naphthol, and the like, or a combination comprisingat least one of the foregoing.

Diethers, including hydrogenated and nonhydrogenated, and substitutedand unsubstituted pyrans, may also be used as stabilizing additives.When present, substituents may include C₁-C₈ alkyl, C₁-C₈ alkyl ether,or C₆-C₂₀ aryl. The pyrans may have substituents including C₁-C₂₀ alkyl,C₆-C₂₀ aryl, C₁-C₂₀ alkoxy, or C₆-C₂₀ aryloxy, and which may bepositioned on any carbon of the pyran ring. Specifically usefulsubstituent groups include C₁-C₂₀ alkoxy or C₆-C₂₀ aryloxy, located onthe ring at the six position. Hydrogenated pyrans are specificallyuseful. Examples of suitable diethers include dihydropyranyl ethers andtetrahydropyranyl ethers.

Nitrogen compounds which may function as stabilizers include highmolecular weight oxamide phenolics, for example, 2,2-oxamido bis-[ethyl3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], high molecular weightoxalic anilides and their derivatives, and amine compounds such asthiourea.

Ionizing radiation stabilizing additives are typically used in amountsof 0.001 to 1 wt %, specifically 0.005 to 0.75 wt %, more specifically0.01 to 0.5 wt %, and still more specifically 0.05 to 0.25 wt %, basedon the total weight of the sulfonate end-capped polycarbonate and anyadded polycarbonate. In an embodiment, a specifically suitable ionizingradiation stabilizing additive is an aliphatic diol.

The thermoplastic composition may further comprise a hydrolysisstabilizer. Typical hydrolysis stabilizers may includecarbodiimide-based additives such as aromatic and/or cycloaliphaticmonocarbo-diimides substituted in position 2 and 2′, such as2,2′,6,6′-tetraisopropyldiphenylcarbodiimide. Polycarbodiimides having amolecular weight of over 500 grams per mole are also suitable. Othercompounds useful as hydrolysis stabilizers include an epoxy modifiedacrylic oligomers or polymers, and oligomers based on cycloaliphaticepoxides. Specific examples of suitable epoxy functionalized stabilizersinclude Cycloaliphatic Epoxide Resin ERL-4221 supplied by Union CarbideCorporation (a subsidiary of Dow Chemical), Danbury, Conn.; and JONCRYL®ADR-4300 and JONCRYL® ADR-4368, available from Johnson Polymer Inc,Sturtevant, Wis. Hydrolysis stabilizers can be used in amounts of 0.001to 1 wt %, specifically 0.01 to 0.5 wt %, and more specifically 0.1 to0.3 wt %, based on the total weight of the sulfonate end-cappedpolycarbonate and any added polycarbonate.

As discussed above, when exposed to gamma radiation, polycarbonatesbecome yellowed in color, with the degree of yellowness increasing withincreasing exposure dose of the gamma radiation. At sufficiently highradiation doses, the yellow color may become sufficiently dark that anarticle prepared from the polycarbonate is compromised in itsusefulness. Likewise, with increasing gamma radiation doses,transparency decreases. Blue and/or violet colorants have also beenadded to polycarbonate compositions in order to offset the yellownessresulting from the sterilization, such that compositions comprising acolorant and articles molded from them may be visibly blue or violetshaded. However, color compensation may not be effective for obtainingcolorless parts as the dose of ionizing radiation is increased. Inaddition, the amount of colorant added to the resin is often selectedfor a given radiation dose, and thus variation of exposure dose due toprocess variability or re-sterilization may cause visible colordifferences between sterilized articles.

Without wishing to be bound by theory, it is believed that exposure togamma radiation generates free radical breakdown products of thepolycarbonate which can react to form species with extended pi-bondconjugation, and that therefore have a yellow color. Stabilizers can beincluded in the polycarbonate and used to stabilize or react with theseradical species, thus slowing the degradation of polycarbonates, butnone appear to be sufficiently active to completely prevent yellowing.The yellowness index of a polycarbonate without an ionizing radiationstabilizing additive after exposure to a total gamma radiation dose of83 kGy is typically greater than about 50, compared with a yellownessindex value of less than 1 for the composition before exposure.Similarly, the loss in transparency of an unstabilized polycarbonatetreated with the same gamma radiation dose can be greater than or equalto about 15%.

The use of other types of stabilizers, such as those based on photoacidgenerators that produce sulfonic acids, in particular monofunctionalphotoacid generators or difunctional photoacid generators havingstraight-chain (i.e., unbranched) alkyl or polyether groups that producesulfonic acids (1 or 2 equivalents of acid per molecule of photoacidgenerator) have been found to require loadings of the stabilizer inexcess of 0.5% by weight of the composition. Increased amounts ofgenerated acid can lead to the formation of other breakdown products inthe polycarbonate, thus potentially causing additional degradation ofthe polycarbonate and mitigating the effectiveness of the stabilizer.Additives having aromatic or benzylic oxy and/or carbonyl groups, andwith or without alcohol functional groups present, have been includedwith such prior art mono- and di-functional photoacid generators toimprove their performance. However, the use of such additives is notdesirable for various reasons of cost, volatility, and concerns abouthandling, specifically for odor threshold and workplace exposure.Brominated compounds such as, for example, brominated bisphenol A, havealso been found to be useful for reducing yellowing of polycarbonatecompounds. However, concerns about the environmental impacts of halidessuch as bromine make this class of compounds less desirable to use.

Surprisingly, it has been found that a sulfonate end-cappedpolycarbonate as described herein can be used to make a thermoplasticcomposition that has significantly improved resistance to yellowing uponexposure to gamma radiation. The presence of the sulfonate end groups inthe sulfonate end-capped polycarbonate provides a high degree ofstability in a thermoplastic composition comprising polycarbonate uponexposure to gamma radiation, per unit of sulfonate end group used, thanobserved with the aforementioned prior art stabilizers. A loading as lowas 0.001 mmol/Kg of the sulfonate end group based on the total weight ofthe sulfonate end-capped polycarbonate and any non-sulfonate end-cappedpolycarbonate can accomplish this. Such low loadings of substitutedaromatic composition can allow the preparation of thermoplasticcompositions with low color (i.e., without added pigment or dye) usefulfor making articles wherein the article has a thickness of 3.2±0.12millimeters and a transmission of greater than 95% according to ASTMD1003-00, and wherein these properties are maintained after gammairradiation at a total dose of up to 83 kGy.

Advantageously, the sulfonate end-capped polycarbonate is a polymer. Useof polymeric compounds as stabilizers for reducing yellowing can providemore uniform mixing and blending of the added in higher quantities(typically greater than or equal to about 10 w % of the combined weightsof sulfonate end-capped polycarbonate and any added polycarbonate). Inaddition, in an embodiment, the sulfonate end-capped polycarbonate maydesirably prepared at low cost by adding a suitable reactive sulfonicacid derivative to a reaction used to prepare a polycarbonate.

Without wishing to be bound by theory, it is believed that the sulfonateend-capped polycarbonates disclosed herein generate active radicalspecies more efficiently than the prior art mono- or disubstitutedaromatic compounds, and thereby provide a higher concentration of activeradicals per unit of gamma radiation energy absorbed. Under this theory,these active radicals are believed to neutralize reactive speciesgenerated from polycarbonates, which would otherwise lead topolycarbonate degradation products that can lead to increased yellownessin the polycarbonate. Including an ionizing radiation stabilizingadditive, for example an aliphatic diol, with the sulfonate end-cappedpolycarbonate and any added polycarbonate, can provide an additionalsynergistic improvement in resistance to increase in yellowness. Theamounts and identities of the sulfonate end-capped polycarbonate; anypolymers where included such as polycarbonate; and additives such asionizing radiation stabilizing additive, are selected such that theincrease in the yellowness of an article molded from the thermoplasticcomposition prepared therewith is minimized after gamma radiationexposure.

The increase in yellowness of a thermoplastic composition after gammaradiation exposure may be determined by measuring the yellowness index(YI) of a molded article prepared from the thermoplastic composition,and comparing to the YI of the article before exposure. The YI of themolded article can be measured using transmittance and/or reflectivespectroscopic methods depending upon the combination of transparency,color, and surface finish appearance of the article. Where a moldedarticle prepared from the thermoplastic composition is eithertransparent or translucent; is colorless, white, or off-white; and isglossy, semi-glossy, or non-glossy, the YI of the molded article may bedetermined according to ASTM D1925-70. Where the molded article isopaque; is off-white or non-white; and has a glossy surface finish, theYI may be determined using reflectance measurement according to ASTME313-73. Generally, higher doses of ionizing radiation give largerincreases in measured yellowness index, and lower doses of ionizingradiation give smaller increases in yellowness index. It has beenobserved that the increase in measured yellowness index in thethermoplastic compositions does not necessarily increase linearly withincreasing dose. The thermoplastic composition from which the articlefor testing is molded can contain additives including ionizing radiationstabilizing additives, and other additives typically included withpolycarbonates, such as mold release agents and antioxidants, whereinthe presence of these additives in an amount effective to perform theintended function does not significantly adversely affect the desiredproperties of the thermoplastic composition. Typically the total amountof these additives is less than 1.0 percent by weight of the totalweight of components present in thermoplastic composition. In anexemplary embodiment, additives present in the thermoplastic compositionused to prepare a molded article for yellowness testing may include 0.15weight percent of 2-methyl-2,4-pentanediol as aliphatic diol, 0.27weight percent pentaerythritol tetrastearate as a mold release agent,and 0.027 weight percent of 2,6-di-tert-butylphenyl)phosphite asantioxidant.

Thus, in an embodiment, a molded article having a thickness of 3.2±0.12millimeters and consisting of the sulfonate end-capped polycarbonate, apolycarbonate, and an effective amount (for the purposes of this test,defined herein as less than 1.0 wt % of the total weight of the article)of each of an aliphatic diol, a mold-release agent, and an antioxidanthas, after exposure to a total gamma radiation dose of 83 kGy and whenmeasured according to ASTM D1925-70, an increase in yellowness index(dYI) of less than or equal to 36, specifically less than or equal to30, more specifically less than or equal to 25, and still morespecifically less than or equal to 20, when compared to the unexposedarticle.

In another embodiment, a molded article having a thickness of 3.2±0.12millimeters and consisting of the sulfonate end-capped polycarbonate, apolycarbonate, and an effective amount of each of an aliphatic diol, amold-release agent, and an antioxidant has, after exposure to a totalgamma radiation dose of 81 kGy and when measured according to ASTMD1925-70, an increase in yellowness index (dYI) of less than or equal to24, specifically less than or equal to 20, more specifically less thanor equal to 18, and still more specifically less than or equal to 17,when compared to the unexposed article.

In another embodiment, a molded article having a thickness of 3.2±0.12millimeters and consisting of the sulfonate end-capped polycarbonate, apolycarbonate, and an effective amount of each of an aliphatic diol, amold-release agent, and an antioxidant has, after exposure to a totalgamma radiation dose of 51 kGy and when measured according to ASTMD1925-70, an increase in yellowness index (dYI) of less than or equal to14.5, specifically less than or equal to 14.0, more specifically lessthan or equal to 13.0, and still more specifically less than or equal to12.0, when compared to the unexposed article.

In another embodiment, a molded article having a thickness of 3.2±0.12millimeters and consisting of the sulfonate end-capped polycarbonate, apolycarbonate, and an effective amount of each of an aliphatic diol, amold-release agent, and an antioxidant has, after exposure to a totalgamma radiation dose of 30 kGy and when measured according to ASTMD1925-70, an increase in yellowness index (dYI) of less than or equal to7.5, specifically less than or equal to 7.3, more specifically less thanor equal to 7.0, and still more specifically less than or equal to 6.7,when compared to the unexposed article.

In addition to the sulfonate end-capped polycarbonate, polycarbonateand/or other resins, and where desired, ionizing radiation stabilizingadditive and/or hydrolysis stabilizer, the thermoplastic composition mayinclude various other additives ordinarily incorporated withthermoplastic compositions of this type, with the proviso that theadditives are selected so as not to adversely affect the desiredproperties of the thermoplastic composition. Mixtures of additives maybe used. Such additives may be mixed at a suitable time during themixing of the components for forming the thermoplastic composition.

The thermoplastic composition may comprise a colorant such as a pigmentand/or dye additive. Suitable pigments include for example, inorganicpigments such as metal oxides and mixed metal oxides such as zinc oxide,titanium dioxides, iron oxides or the like; sulfides such as zincsulfides, or the like; aluminates; sodium sulfo-silicates, sulfates,chromates, or the like; carbon blacks; zinc ferrites; ultramarine blue;Pigment Brown 24; Pigment Red 101; Pigment Yellow 119; organic pigmentssuch as azos, di-azos, quinacridones, perylenes, naphthalenetetracarboxylic acids, flavanthrones, isoindolinones,tetrachloroisoindolinones, anthraquinones, anthanthrones, dioxazines,phthalocyanines, and azo lakes; Pigment Blue 60, Pigment Red 122,Pigment Red 149, Pigment Red 177, Pigment Red 179, Pigment Red 202,Pigment Violet 29, Pigment Blue 15, Pigment Blue 15:4, Pigment Blue 28,Pigment Green 7, Pigment Yellow 147 and Pigment Yellow 150, orcombinations comprising at least one of the foregoing pigments. Pigmentscan be used in amounts of 0.01 to 10 percent by weight, based on thetotal weight of the sulfonate end-capped polycarbonate and any addedpolycarbonate.

Suitable dyes can be organic materials and include, for example,coumarin dyes such as coumarin 460 (blue), coumarin 6 (green), nile redor the like; lanthanide complexes; hydrocarbon and substitutedhydrocarbon dyes; polycyclic aromatic hydrocarbon dyes; scintillationdyes such as oxazole or oxadiazole dyes; aryl- or heteroaryl-substitutedpoly(C₂₋₈) olefin dyes; carbocyanine dyes; indanthrone dyes;phthalocyanine dyes; oxazine dyes; carbostyryl dyes;napthalenetetracarboxylic acid dyes; porphyrin dyes; bis(styryl)biphenyldyes; acridine dyes; anthraquinone dyes; cyanine dyes; methine dyes;arylmethane dyes; azo dyes; indigoid dyes, thioindigoid dyes, diazoniumdyes; nitro dyes; quinone imine dyes; aminoketone dyes; tetrazoliumdyes; thiazole dyes; perylene dyes, perinone dyes;bis-benzoxazolylthiophene (BBOT); triarylmethane dyes; xanthene dyes;thioxanthene dyes; naphthalimide dyes; lactone dyes; fluorophores suchas anti-stokes shift dyes which absorb in the near infrared wavelengthand emit in the visible wavelength, or the like; luminescent dyes suchas 7-amino-4-methylcoumarin;3-(2′-benzothiazolyl)-7-diethylaminocoumarin;2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole;2,5-bis-(4-biphenylyl)-oxazole; 2,2′-dimethyl-p-quaterphenyl;2,2-dimethyl-p-terphenyl; 3,5,3 ″″,5″″-tetra-t-butyl-p-quinquephenyl;2,5-diphenylfuran; 2,5-diphenyloxazole; 4,4′-diphenylstilbene;4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran;1,1′-diethyl-2,2′-carbocyanine iodide;3,3′-diethyl-4,4′,5,5′-dibenzothiatricarbocyanine iodide;7-dimethylamino-1-methyl-4-methoxy-8-azaquinolone-2;7-dimethylamino-4-methylquinolone-2;2-(4-(4-dimethylaminophenyl)-1,3-butadienyl)-3-ethylbenzothiazoliumperchlorate; 3-diethylamino-7-diethyliminophenoxazonium perchlorate;2-(1-naphthyl)-5-phenyloxazole; 2,2′-p-phenylen-bis(5-phenyloxazole);rhodamine 700; rhodamine 800; pyrene; chrysene; rubrene; coronene, orthe like, or combinations comprising at least one of the foregoing dyes.Where it is desirable to use organic dyes and pigments, the dyes may bescreened to determine their sensitivity to gamma radiation at a givenexposure dose or range of exposure doses. Dyes can be used in amounts of0.01 to 10 percent by weight, based on the total weight of the sulfonateend-capped polycarbonate and any added polycarbonate.

The thermoplastic composition may include an impact modifier to increaseits impact resistance, where the impact modifier is present in an amountthat does not adversely affect the desired properties of thethermoplastic composition. These impact modifiers includeelastomer-modified graft copolymers comprising (i) an elastomeric (i.e.,rubbery) polymer substrate having a Tg less than 10° C., morespecifically less than −10° C., or more specifically −40° to −80° C.,and (ii) a rigid polymeric superstrate grafted to the elastomericpolymer substrate. As is known, elastomer-modified graft copolymers maybe prepared by first providing the elastomeric polymer, thenpolymerizing the constituent monomer(s) of the rigid phase in thepresence of the elastomer to obtain the graft copolymer. The grafts maybe attached as graft branches or as shells to an elastomer core. Theshell may merely physically encapsulate the core, or the shell may bepartially or essentially completely grafted to the core.

Suitable materials for use as the elastomer phase include, for example,conjugated diene rubbers; copolymers of a conjugated diene with lessthan 50 wt % of a copolymerizable monomer; olefin rubbers such asethylene propylene copolymers (EPR) or ethylene-propylene-diene monomerrubbers (EPDM); ethylene-vinyl acetate rubbers; silicone rubbers;elastomeric C₁₋₈ alkyl(meth)acrylates; elastomeric copolymers of C₁₋₈alkyl(meth)acrylates with butadiene and/or styrene; or combinationscomprising at least one of the foregoing elastomers.

Suitable conjugated diene monomers for preparing the elastomer phase areof formula (21):

wherein each X^(b) is independently hydrogen, C₁-C₅ alkyl, or the like.Examples of conjugated diene monomers that may be used are butadiene,isoprene, 1,3-heptadiene, methyl-1,3-pentadiene,2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-pentadiene; 1,3- and2,4-hexadienes, and the like, as well as mixtures comprising at leastone of the foregoing conjugated diene monomers. Specific conjugateddiene homopolymers include polybutadiene and polyisoprene.

Copolymers of a conjugated diene rubber may also be used, for examplethose produced by aqueous radical emulsion polymerization of aconjugated diene and one or more monomers copolymerizable therewith.Vinyl aromatic compounds may be copolymerized with the ethylenicallyunsaturated nitrile monomer to form a copolymer, wherein thevinylaromatic compounds can include monomers of formula (22):

wherein each X^(c) is independently hydrogen, C₁-C₁₂ alkyl, C₃-C₁₂cycloalkyl, C₆-C₁₂ aryl, C₇-C₁₂ arylalkyl, C₇-C₁₋₂ alkylaryl, C₁-C₁₂alkoxy, C₃-C₁₂ cycloalkoxy, C₆-C₁₂ aryloxy, chloro, bromo, or hydroxy,and R is hydrogen, C₁-C₅ alkyl, bromo, or chloro. Examples of suitablemonovinylaromatic monomers that may be used include styrene,3-methylstyrene, 3,5-diethylstyrene, 4-n-propylstyrene,alpha-methylstyrene, alpha-methyl vinyltoluene, alpha-chlorostyrene,alpha-bromostyrene, dichlorostyrene, dibromostyrene,tetra-chlorostyrene, and the like, and combinations comprising at leastone of the foregoing compounds. Styrene and/or alpha-methylstyrene maybe used as monomers copolymerizable with the conjugated diene monomer.

Other monomers that may be copolymerized with the conjugated diene aremonovinylic monomers such as itaconic acid, acrylamide, N-substitutedacrylamide or methacrylamide, maleic anhydride, maleimide, N-alkyl-,aryl-, or haloaryl-substituted maleimide, glycidyl(meth)acrylates, andmonomers of the generic formula (23):

wherein R is hydrogen, C₁-C₅ alkyl, bromo, or chloro, and X^(c) isC₁-C₁₂ alkoxycarbonyl, C₁-C₁₂ aryloxycarbonyl, hydroxy carbonyl, or thelike. Examples of monomers of formula (21) include, acrylic acid,methyl(meth)acrylate, ethyl (meth)acrylate, n-butyl(meth)acrylate,t-butyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate,2-ethylhexyl(meth)acrylate, and the like, and combinations comprising atleast one of the foregoing monomers. Monomers such as n-butyl acrylate,ethyl acrylate, and 2-ethylhexyl acrylate are commonly used as monomerscopolymerizable with the conjugated diene monomer. Mixtures of theforegoing monovinyl monomers and monovinylaromatic monomers may also beused.

Suitable (meth)acrylate monomers suitable for use as the elastomericphase may be cross-linked, particulate emulsion homopolymers orcopolymers of C₁₋₈ alkyl(meth)acrylates, in particular C₄₋₆ alkylacrylates, for example n-butyl acrylate, t-butyl acrylate, n-propylacrylate, isopropyl acrylate, 2-ethylhexyl acrylate, and the like, andcombinations comprising at least one of the foregoing monomers. The C₁₋₈alkyl (meth)acrylate monomers may optionally be polymerized in admixturewith up to 15 wt % of comonomers of formulas (21), (22), or (23).Exemplary comonomers include but are not limited to butadiene, isoprene,styrene, methyl methacrylate, phenyl methacrylate, penethylmethacrylate,N-cyclohexylacrylamide, vinyl methyl ether, and mixtures comprising atleast one of the foregoing comonomers. Optionally, up to 5 wt % apolyfunctional crosslinking comonomer may be present, for exampledivinylbenzene, alkylenediol di(meth)acrylates such as glycolbisacrylate, alkylenetriol tri(meth)acrylates, polyesterdi(meth)acrylates, bisacrylamides, triallyl cyanurate, triallylisocyanurate, allyl(meth)acrylate, diallyl maleate, diallyl fumarate,diallyl adipate, triallyl esters of citric acid, triallyl esters ofphosphoric acid, and the like, as well as combinations comprising atleast one of the foregoing crosslinking agents.

The elastomer phase may be polymerized by mass, emulsion, suspension,solution or combined processes such as bulk-suspension, emulsion-bulk,bulk-solution or other techniques, using continuous, semibatch, or batchprocesses. The particle size of the elastomer substrate is not critical.For example, an average particle size of 0.001 to 25 micrometers,specifically 0.01 to 15 micrometers, or even more specifically 0.1 to 8micrometers may be used for emulsion based polymerized rubber lattices.A particle size of 0.5 to 10 micrometers, specifically 0.6 to 1.5micrometers may be used for bulk polymerized rubber substrates. Particlesize may be measured by simple light transmittance methods or capillaryhydrodynamic chromatography (CHDF). The elastomer phase may be aparticulate, moderately cross-linked conjugated butadiene or C₄₋₆ alkylacrylate rubber, and preferably has a gel content greater than 70 wt %.Also suitable are mixtures of butadiene with styrene and/or C₄₋₆ alkylacrylate rubbers.

The elastomeric phase may provide 5 to 95 wt % of the total graftcopolymer, more specifically 20 to 90 wt %, and even more specifically40 to 85 wt % of the elastomer-modified graft copolymer, the remainderbeing the rigid graft phase.

The rigid phase of the elastomer-modified graft copolymer may be formedby graft polymerization of a mixture comprising a monovinylaromaticmonomer and optionally one or more comonomers in the presence of one ormore elastomeric polymer substrates. The above-describedmonovinylaromatic monomers of formula (22) may be used in the rigidgraft phase, including styrene, alpha-methyl styrene, halostyrenes suchas dibromostyrene, vinyltoluene, vinylxylene, butylstyrene,para-hydroxystyrene, methoxystyrene, or the like, or combinationscomprising at least one of the foregoing monovinylaromatic monomers.Suitable comonomers include, for example, the above-describedmonovinylic monomers and/or monomers of the general formula (23). In oneembodiment, R is hydrogen or C₁-C₂ alkyl, and X^(c) is cyano or C₁-C₁₂alkoxycarbonyl. Specific examples of suitable comonomers for use in therigid phase include, methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, and the like, and combinationscomprising at least one of the foregoing comonomers.

The relative ratio of monovinylaromatic monomer and comonomer in therigid graft phase may vary widely depending on the type of elastomersubstrate, type of monovinylaromatic monomer(s), type of comonomer(s),and the desired properties of the impact modifier. The rigid phase maygenerally comprise up to 100 wt % of monovinyl aromatic monomer,specifically 30 to 100 wt %, more specifically 50 to 90 wt %monovinylaromatic monomer, with the balance being comonomer(s).

Depending on the amount of elastomer-modified polymer present, aseparate matrix or continuous phase of ungrafted rigid polymer orcopolymer may be simultaneously obtained along with theelastomer-modified graft copolymer. Typically, such impact modifierscomprise 40 to 95 wt % elastomer-modified graft copolymer and 5 to 65 wt% graft copolymer, based on the total weight of the impact modifier. Inanother embodiment, such impact modifiers comprise 50 to 85 wt %, morespecifically 75 to 85 wt % rubber-modified graft copolymer, togetherwith 15 to 50 wt %, more specifically 15 to 25 wt % graft copolymer,based on the total weight of the impact modifier.

Another specific type of elastomer-modified impact modifier comprisesstructural units derived from at least one silicone rubber monomer, abranched acrylate rubber monomer having the formulaH₂C═C(R^(d))C(O)OCH₂CH₂R^(e), wherein R^(d) is hydrogen or a C₁-C₈linear or branched alkyl group and R^(e) is a branched C₃-C₁₆ alkylgroup; a first graft link monomer; a polymerizable alkenyl-containingorganic material; and a second graft link monomer. The silicone rubbermonomer may comprise, for example, a cyclic siloxane, tetraalkoxysilane,trialkoxysilane, (acryloxy)alkoxysilane, (mercaptoalkyl)alkoxysilane,vinylalkoxysilane, or allylalkoxysilane, alone or in combination, e.g.,decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane,trimethyltriphenylcyclotrisiloxane,tetramethyltetraphenylcyclotetrasiloxane,tetramethyltetravinylcyclotetrasiloxane, octaphenylcyclotetrasiloxane.,octamethylcyclotetrasiloxane and/or tetraethoxysilane.

Exemplary branched acrylate rubber monomers include iso-octyl acrylate,6-methyloctyl acrylate, 7-methyloctyl acrylate, 6-methylheptyl acrylate,and the like, alone or in combination. The polymerizable,alkenyl-containing organic material may be, for example, a monomer offormula (22) or (23), e.g., styrene, alpha-methylstyrene, or anunbranched (meth)acrylate such as methyl methacrylate, 2-ethylhexylmethacrylate, methyl acrylate, ethyl acrylate, n-propyl acrylate, or thelike, alone or in combination.

The at least one first graft link monomer may be an(acryloxy)alkoxysilane, a (mercaptoalkyl)alkoxysilane, avinylalkoxysilane, or an allylalkoxysilane, alone or in combination,e.g., (gamma-methacryloxypropyl) (dimethoxy)methylsilane and/or(3-mercaptopropyl)trimethoxysilane. The at least one second graft linkmonomer is a polyethylenically unsaturated compound having at least oneallyl group, such as allyl methacrylate, triallyl cyanurate, or triallylisocyanurate, alone or in combination.

The silicone-acrylate impact modifier compositions can be prepared byemulsion polymerization, wherein, for example at least one siliconerubber monomer is reacted with at least one first graft link monomer ata temperature from 30° C. to 110° C. to form a silicone rubber latex, inthe presence of a surfactant such as dodecylbenzenesulfonic acid.Alternatively, a cyclic siloxane such as cyclooctamethyltetrasiloxaneand tetraethoxyorthosilicate may be reacted with a first graft linkmonomer such as (gamma-methacryloxypropyl)methyldimethoxysilane, toafford silicone rubber having an average particle size from 100nanometers to 2 micrometers. At least one branched acrylate rubbermonomer is then polymerized with the silicone rubber particles,optionally in presence of a cross linking monomer, such asallylmethacrylate in the presence of a free radical generatingpolymerization catalyst such as benzoyl peroxide. This latex is thenreacted with a polymerizable alkenyl-containing organic material and asecond graft link monomer. The latex particles of the graftsilicone-acrylate rubber hybrid may be separated from the aqueous phasethrough coagulation (by treatment with a coagulant) and dried to a finepowder to produce the silicone-acrylate rubber impact modifiercomposition. This method can be generally used for producing thesilicone-acrylate impact modifier having a particle size from 100nanometers to 2 micrometers.

Processes known for the formation of the foregoing elastomer-modifiedgraft copolymers include mass, emulsion, suspension, and solutionprocesses, or combined processes such as bulk-suspension, emulsion-bulk,bulk-solution or other techniques, using continuous, semibatch, or batchprocesses.

The foregoing types of impact modifiers, including SAN copolymers, canbe prepared by an emulsion polymerization process that is free of basicmaterials such as alkali metal salts of C₆₋₃₀ fatty acids, for examplesodium stearate, lithium stearate, sodium oleate, potassium oleate, andthe like; alkali metal carbonates, amines such as dodecyl dimethylamine, dodecyl amine, and the like; and ammonium salts of amines. Suchmaterials are commonly used as surfactants in emulsion polymerization,and may catalyze transesterification and/or degradation ofpolycarbonates. Instead, ionic sulfate, sulfonate or phosphatesurfactants may be used in preparing the impact modifiers, particularlythe elastomeric substrate portion of the impact modifiers. Suitablesurfactants include, for example, C₁₋₂₂ alkyl or C₇₋₂₅ alkylarylsulfonates, C₁₋₂₂ alkyl or C₇₋₂₅ alkylaryl sulfates, C₁₋₂₂ alkyl orC₇₋₂₅ alkylaryl phosphates, substituted silicates, and mixtures thereof.A specific surfactant is a C₆₋₁₆, specifically a C₈₋₁₂ alkyl sulfonate.In the practice, any of the above-described impact modifiers may beused.

A specific impact modifier of this type is a methylmethacrylate-butadiene-styrene (MBS) impact modifier wherein thebutadiene substrate is prepared using above-described sulfonates,sulfates, or phosphates as surfactants. Other examples ofelastomer-modified graft copolymers besides ABS and MBS include but arenot limited to acrylonitrile-styrene-butyl acrylate (ASA), methylmethacrylate-acrylonitrile-butadiene-styrene (MABS), andacrylonitrile-ethylene-propylene-diene-styrene (AES). When present,impact modifiers can be present in the thermoplastic composition inamounts of 0.1 to 30 percent by weight, based on the total weight of thesulfonate end-capped polycarbonate and any added polycarbonate.

The thermoplastic composition may include fillers or reinforcing agents.The fillers and reinforcing agents may desirably be in the form ofnanoparticles, i.e., particles with a median particle size (D₅₀) smallerthan 100 nm as determined using light scattering methods. Where used,suitable fillers or reinforcing agents include, for example, silicatesand silica powders such as aluminum silicate (mullite), syntheticcalcium silicate, zirconium silicate, fused silica, crystalline silicagraphite, natural silica sand, or the like; boron powders such asboron-nitride powder, boron-silicate powders, or the like; oxides suchas TiO₂, aluminum oxide, magnesium oxide, or the like; calcium sulfate(as its anhydride, dihydrate or trihydrate); calcium carbonates such aschalk, limestone, marble, synthetic precipitated calcium carbonates, orthe like; talc, including fibrous, modular, needle shaped, lamellartalc, or the like; wollastonite; surface-treated wollastonite; glassspheres such as hollow and solid glass spheres, silicate spheres,cenospheres, aluminosilicate (atmospheres), or the like; kaolin,including hard kaolin, soft kaolin, calcined kaolin, kaolin comprisingvarious coatings known in the art to facilitate compatibility with thepolymeric matrix resin, or the like; single crystal fibers or “whiskers”such as silicon carbide, alumina, boron carbide, iron, nickel, copper,or the like; fibers (including continuous and chopped fibers) such asasbestos, carbon fibers, glass fibers, such as E, A, C, ECR, R, S, D, orNE glasses, or the like; sulfides such as molybdenum sulfide, zincsulfide or the like; barium compounds such as barium titanate, bariumferrite, barium sulfate, heavy spar, or the like; metals and metaloxides such as particulate or fibrous aluminum, bronze, zinc, copper andnickel or the like; flaked fillers such as glass flakes, flaked siliconcarbide, aluminum diboride, aluminum flakes, steel flakes or the like;fibrous fillers, for example short inorganic fibers such as thosederived from blends comprising at least one of aluminum silicates,aluminum oxides, magnesium oxides, and calcium sulfate hemihydrate orthe like; natural fillers and reinforcements, such as wood flourobtained by pulverizing wood, fibrous products such as cellulose,cotton, sisal, jute, starch, cork flour, lignin, ground nut shells,corn, rice grain husks or the like; organic fillers such aspolytetrafluoroethylene; reinforcing organic fibrous fillers formed fromorganic polymers capable of forming fibers such as poly(ether ketone),polyimide, polybenzoxazole, poly(phenylene sulfide), polyesters,polyethylene, aromatic polyamides, aromatic polyimides, polyetherimides,polytetrafluoroethylene, acrylic resins, poly(vinyl alcohol) or thelike; as well as additional fillers and reinforcing agents such as mica,clay, feldspar, flue dust, fillite, quartz, quartzite, perlite, tripoli,diatomaceous earth, carbon black, or the like, or combinationscomprising at least one of the foregoing fillers or reinforcing agents.

The fillers and reinforcing agents may be coated with a layer ofmetallic material to facilitate conductivity, or surface treated withsilanes to improve adhesion and dispersion with the polymeric matrixresin. In addition, the reinforcing fillers may be provided in the formof monofilament or multifilament fibers and may be used either alone orin combination with other types of fiber, through, for example,co-weaving or core/sheath, side-by-side, orange-type or matrix andfibril constructions, or by other methods known to one skilled in theart of fiber manufacture. Suitable cowoven structures include, forexample, glass fiber-carbon fiber, carbon fiber-aromaticpolyimide(aramid) fiber, and aromatic polyimide fiberglass fiber or thelike. Fibrous fillers may be supplied in the form of, for example,rovings, woven fibrous reinforcements, such as 0-90 degree fabrics orthe like; non-woven fibrous reinforcements such as continuous strandmat, chopped strand mat, tissues, papers and felts or the like; orthree-dimensional reinforcements such as braids. Fillers can be used inamounts of 0 to 90 percent by weight, based on the total weight of thesulfonate end-capped polycarbonate and any added polycarbonate.

Suitable antioxidant additives include, for example, organophosphitessuch as tris(nonyl phenyl)phosphite,tris(2,4-di-t-butylphenyl)phosphite,bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, distearylpentaerythritol diphosphite or the like; alkylated monophenols orpolyphenols; alkylated reaction products of polyphenols with dienes,such as tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane, or the like; butylated reaction products of para-cresol ordicyclopentadiene; alkylated hydroquinones; hydroxylated thiodiphenylethers; alkylidene-bisphenols; benzyl compounds; esters ofbeta-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid with monohydricor polyhydric alcohols; esters ofbeta-(5-tert-butyl-4-hydroxy-3-methylphenyl)-propionic acid withmonohydric or polyhydric alcohols; esters of thioalkyl or thioarylcompounds such as distearylthiopropionate, dilaurylthiopropionate,ditridecylthiodipropionate,octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,pentaerythrityl-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionateor the like; amides ofbeta-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid or the like, orcombinations comprising at least one of the foregoing antioxidants.Antioxidants can be used in amounts of 0.0001 to 1 percent by weight,based on the total weight of the sulfonate end-capped polycarbonate andany added polycarbonate.

Suitable heat stabilizer additives include, for example,organophosphites such as triphenyl phosphite,tris-(2,6-dimethylphenyl)phosphite, tris-(mixed mono- anddi-nonylphenyl)phosphite or the like; phosphonates such asdimethylbenzene phosphonate or the like, phosphates such as trimethylphosphate, or the like, or combinations comprising at least one of theforegoing heat stabilizers. Heat stabilizers can be used in amounts of0.0001 to 1 percent by weight, based on the total weight of thesulfonate end-capped polycarbonate and any added polycarbonate.

Light stabilizers and/or ultraviolet light (UV) absorbing additives mayalso be used. Suitable light stabilizer additives include, for example,benzotriazoles such as 2-(2-hydroxy-5-methylphenyl)benzotriazole,2-(2-hydroxy-5-tert-octylphenyl)-benzotriazole and 2-hydroxy-4-n-octoxybenzophenone, or the like, or combinations comprising at least one ofthe foregoing light stabilizers. Light stabilizers can be used inamounts of 0.0001 to 1 percent by weight, based on the total weight ofthe sulfonate end-capped polycarbonate and any added polycarbonate.

Suitable UV absorbing additives include for example,hydroxybenzophenones; hydroxybenzotriazoles; hydroxybenzotriazines;cyanoacrylates; oxanilides; benzoxazinones;2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)-phenol (CYASORB®5411); 2-hydroxy-4-n-octyloxybenzophenone (CYASORB® 531);2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-(octyloxy)-phenol(CYASORB® 1164); 2,2′-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one)(CYASORB® UV-3638);1,3-bis[(2-cyano-3,3-diphenylacryloyl)oxy]-2,2-bis[[(2-cyano-3,3-diphenylacryloyl)oxy]methyl]propane(UVINUL® 3030); 2,2′-(1,4-phenylene) bis(4H-3,1-benzoxazin-4-one);1,3-bis[(2-cyano-3,3-diphenylacryloyl)oxy]-2,2-bis[[(2-cyano-3,3-diphenylacryloyl)oxy]methyl]propane; nano-size inorganic materials such as titanium oxide, ceriumoxide, and zinc oxide, all with particle size less than 100 nanometers;or the like, or combinations comprising at least one of the foregoing UVabsorbers. UV absorbers can be used in amounts of 0.0001 to 1 percent byweight, based on the total weight of the sulfonate end-cappedpolycarbonate and any added polycarbonate.

Plasticizers, lubricants, and/or mold release agents additives may alsobe used. There is considerable overlap among these types of materials,which include, for example, phthalic acid esters such asdioctyl-4,5-epoxy-hexahydrophthalate;tris-(octoxycarbonylethyl)isocyanurate; tristearin; di- orpolyfunctional aromatic phosphates such as resorcinol tetraphenyldiphosphate (RDP), the bis(diphenyl)phosphate of hydroquinone and thebis(diphenyl)phosphate of bisphenol-A; poly-alpha-olefins; epoxidizedsoybean oil; silicones, including silicone oils; esters, for example,fatty acid esters such as alkyl stearyl esters, e.g., methyl stearate;stearyl stearate, pentaerythritol tetrastearate, and the like; mixturesof methyl stearate and hydrophilic and hydrophobic nonionic surfactantscomprising polyethylene glycol polymers, polypropylene glycol polymers,and copolymers thereof, e.g., methyl stearate andpolyethylene-polypropylene glycol copolymers in a suitable solvent;waxes such as beeswax, montan wax, paraffin wax or the like. Suchmaterials can be used in amounts of 0.001 to 1 percent by weight,specifically 0.01 to 0.75 percent by weight, more specifically 0.1 to0.5 percent by weight, based on the total weight of the sulfonateend-capped polycarbonate and any added polycarbonate.

The term “antistatic agent” refers to monomeric, oligomeric, orpolymeric materials that can be processed into polymer resins and/orsprayed onto materials or articles to improve conductive properties andoverall physical performance. Examples of monomeric antistatic agentsinclude glycerol monostearate, glycerol distearate, glyceroltristearate, ethoxylated amines, primary, secondary and tertiary amines,ethoxylated alcohols, alkyl sulfates, alkylarylsulfates,alkylphosphates, alkylaminesulfates, alkyl sulfonate salts such assodium stearyl sulfonate, sodium dodecylbenzenesulfonate or the like,quaternary ammonium salts, quaternary ammonium resins, imidazolinederivatives, sorbitan esters, ethanolamides, betaines, or the like, orcombinations comprising at least one of the foregoing monomericantistatic agents.

Exemplary polymeric antistatic agents include certain polyesteramidespolyether-polyamide(polyetheramide) block copolymers,polyetheresteramide block copolymers, polyetheresters, or polyurethanes,each containing polyalkylene glycol moieties polyalkylene oxide unitssuch as polyethylene glycol, polypropylene glycol, polytetramethyleneglycol, and the like. Such polymeric antistatic agents are commerciallyavailable, for example Pelestat® 6321 (Sanyo) or Pebax® MH1657(Atofina), Irgastat® P18 and P22 (Ciba-Geigy). Other polymeric materialsthat may be used as antistatic agents are inherently conducting polymerssuch as polyaniline (commercially available as PANIPOL®EB from Panipol),polypyrrole, and polythiophenes such as for examplepoly(3,4-ethylenedioxythiophene) (commercially available from H. C.Stark), which retain some of their intrinsic conductivity after meltprocessing at elevated temperatures. In one embodiment, carbon fibers,carbon nanofibers, carbon nanotubes, carbon black, or any combination ofthe foregoing may be used in a polymeric resin containing chemicalantistatic agents to render the composition electrostaticallydissipative. Antistatic agents can be used in amounts of 0.0001 to 5percent by weight, based on the total weight of the sulfonate end-cappedpolycarbonate and any added polycarbonate.

Suitable flame retardant that may be added may be organic compounds thatinclude phosphorus, bromine, and/or chlorine. Non-brominated andnon-chlorinated phosphorus-containing flame retardants may be preferredin certain applications for regulatory reasons, for example organicphosphates and organic compounds containing phosphorus-nitrogen bonds.

One type of exemplary organic phosphate is an aromatic phosphate of theformula (GO)₃P═O, wherein each G is independently an alkyl, cycloalkyl,aryl, alkylaryl, or arylalkyl group, provided that at least one G is anaromatic group. Two of the G groups may be joined together to provide acyclic group, for example, diphenyl pentaerythritol diphosphate. Othersuitable aromatic phosphates may be, for example, phenylbis(dodecyl)phosphate, phenyl bis(neopentyl)phosphate, phenylbis(3,5,5′-trimethylhexyl)phosphate, ethyl diphenyl phosphate,2-ethylhexyl di(p-tolyl)phosphate, bis(2-ethylhexyl)p-tolyl phosphate,tritolyl phosphate, bis(2-ethylhexyl)phenyl phosphate,tri(nonylphenyl)phosphate, bis(dodecyl)p-tolyl phosphate, dibutyl phenylphosphate, 2-chloroethyl diphenyl phosphate, p-tolylbis(2,5,5′-trimethylhexyl)phosphate, 2-ethylhexyl diphenyl phosphate, orthe like. A specific aromatic phosphate is one in which each G isaromatic, for example, triphenyl phosphate, tricresyl phosphate,isopropylated triphenyl phosphate, and the like.

Di- or polyfunctional aromatic phosphorus-containing compounds are alsouseful, for example, compounds of the formulas below:

wherein each G¹ is independently a hydrocarbon having 1 to 30 carbonatoms; each G² is independently a hydrocarbon or hydrocarbonoxy having 1to 30 carbon atoms; each X^(a) is independently a hydrocarbon having 1to 30 carbon atoms; each X is independently a bromine or chlorine; m is0 to 4, and n is 1 to 30. Examples of suitable di- or polyfunctionalaromatic phosphorus-containing compounds include resorcinol tetraphenyldiphosphate (RDP), the bis(diphenyl)phosphate of hydroquinone and thebis(diphenyl)phosphate of bisphenol-A, respectively, their oligomericand polymeric counterparts, and the like.

Exemplary suitable flame retardant compounds containingphosphorus-nitrogen bonds include phosphonitrilic chloride, phosphorusester amides, phosphoric acid amides, phosphonic acid amides, phosphinicacid amides, tris(aziridinyl)phosphine oxide. When present,phosphorus-containing flame retardants can be present in amounts of 0.1to 10 percent by weight, based on the total weight of the sulfonateend-capped polycarbonate and any added polycarbonate.

Halogenated materials may also be used as flame retardants, for examplehalogenated compounds and resins of formula (24):

wherein R is an alkylene, alkylidene or cycloaliphatic linkage, e.g.,methylene, ethylene, propylene, isopropylene, isopropylidene, butylene,isobutylene, amylene, cyclohexylene, cyclopentylidene, or the like; oran oxygen ether, carbonyl, amine, or a sulfur containing linkage, e.g.,sulfide, sulfoxide, sulfone, or the like. R can also consist of two ormore alkylene or alkylidene linkages connected by such groups asaromatic, amino, ether, carbonyl, sulfide, sulfoxide, sulfone, or thelike.

Ar and Ar′ in formula (24) are each independently mono- orpolycarbocyclic aromatic groups such as phenylene, biphenylene,terphenylene, naphthylene, or the like.

Y is an organic, inorganic, or organometallic radical, for example:halogen, e.g., chlorine, bromine, iodine, fluorine; ether groups of thegeneral formula OE, wherein E is a monovalent hydrocarbon radicalsimilar to X; monovalent hydrocarbon groups of the type represented byR; or other substituents, e.g., nitro, cyano, and the like, saidsubstituents being essentially inert provided that there is at least oneand preferably two halogen atoms per aryl nucleus.

When present, each X is independently a monovalent hydrocarbon group,for example an alkyl group such as methyl, ethyl, propyl, isopropyl,butyl, decyl, or the like; an aryl groups such as phenyl, naphthyl,biphenyl, xylyl, tolyl, or the like; and arylalkyl group such as benzyl,ethylphenyl, or the like; a cycloaliphatic group such as cyclopentyl,cyclohexyl, or the like. The monovalent hydrocarbon group may itselfcontain inert substituents.

Each d is independently 1 to a maximum equivalent to the number ofreplaceable hydrogens substituted on the aromatic rings comprising Ar orAr′. Each e is independently 0 to a maximum equivalent to the number ofreplaceable hydrogens on R. Each a, b, and c is independently a wholenumber, including 0. When b is not 0, neither a nor c may be 0.Otherwise either a or c, but not both, may be 0. Where b is 0, thearomatic groups are joined by a direct carbon-carbon bond.

The hydroxyl and Y substituents on the aromatic groups, Ar and Ar′, canbe varied in the ortho, meta or para positions on the aromatic rings andthe groups can be in any possible geometric relationship with respect toone another.

Included within the scope of the above formula are bisphenols of whichthe following are representative: 2,2-bis-(3,5-dichlorophenyl)-propane;bis-(2-chlorophenyl)-methane; bis(2,6-dibromophenyl)-methane;1,1-bis-(4-iodophenyl)-ethane; 1,2-bis-(2,6-dichlorophenyl)-ethane;1,1-bis-(2-chloro-4-iodophenyl)ethane;1,1-bis-(2-chloro-4-methylphenyl)-ethane;1,1-bis-(3,5-dichlorophenyl)-ethane;2,2-bis-(3-phenyl-4-bromophenyl)-ethane;2,6-bis-(4,6-dichloronaphthyl)-propane;2,2-bis-(2,6-dichlorophenyl)-pentane;2,2-bis-(3,5-dibromophenyl)-hexane; bis-(4-chlorophenyl)-phenyl-methane;bis-(3,5-dichlorophenyl)-cyclohexylmethane;bis-(3-nitro-4-bromophenyl)-methane;bis-(4-hydroxy-2,6-dichloro-3-methoxyphenyl)-methane; and2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane 2,2bis-(3-bromo-4-hydroxyphenyl)-propane. Also included within the abovestructural formula are: 1,3-dichlorobenzene, 1,4-dibromobenzene,1,3-dichloro-4-hydroxybenzene, and biphenyls such as2,2′-dichlorobiphenyl, polybrominated 1,4-diphenoxybenzene,2,4′-dibromobiphenyl, and 2,4′-dichlorobiphenyl as well as decabromodiphenyl oxide, and the like.

Also useful are oligomeric and polymeric halogenated aromatic compounds,such as a copolycarbonate of bisphenol A and tetrabromobisphenol A and acarbonate precursor, e.g., phosgene. Metal synergists, e.g., antimonyoxide, may also be used with the flame retardant. When present, halogencontaining flame retardants can be present in amounts of 0.1 to 10percent by weight, based on the total weight of the sulfonate end-cappedpolycarbonate and any added polycarbonate.

Inorganic flame retardants may also be used, for example salts of C₂₋₁₆alkyl sulfonate salts such as potassium perfluorobutane sulfonate (Rimarsalt), potassium perfluoroctane sulfonate, tetraethylammoniumperfluorohexane sulfonate, and potassium diphenylsulfone sulfonate, andthe like; salts formed by reacting for example an alkali metal oralkaline earth metal (for example lithium, sodium, potassium, magnesium,calcium and barium salts) and an inorganic acid complex salt, forexample, an oxo-anion, such as alkali metal and alkaline-earth metalsalts of carbonic acid, such as Na₂CO₃, K₂CO₃, MgCO₃, CaCO₃, and BaCO₃or fluoro-anion complexes such as Li₃AlF₆, BaSiF₆, KBF₄, K₃AlF₆, KAlF₄,K₂SiF₆, and/or Na₃AlF₆ or the like. When present, inorganic flameretardant salts can be present in amounts of 0.1 to 5 percent by weight,based on the total weight of the sulfonate end-capped polycarbonate andany added polycarbonate.

Anti-drip agents may also be used, for example a fibril forming ornon-fibril forming fluoropolymer such as polytetrafluoroethylene (PTFE).The anti-drip agent may be encapsulated by a rigid copolymer asdescribed above, for example styrene-acrylonitrile copolymer (SAN). PTFEencapsulated in SAN is known as TSAN. Encapsulated fluoropolymers may bemade by polymerizing the encapsulating polymer in the presence of thefluoropolymer, for example an aqueous dispersion. TSAN may providesignificant advantages over PTFE, in that TSAN may be more readilydispersed in the composition. A suitable TSAN may comprise, for example,50 wt % PTFE and 50 wt % SAN, based on the total weight of theencapsulated fluoropolymer. The SAN may comprise, for example, 75 wt %styrene and 25 wt % acrylonitrile based on the total weight of thecopolymer. Alternatively, the fluoropolymer may be pre-blended in somemanner with a second polymer, such as for, example, an aromaticpolycarbonate resin or SAN to form an agglomerated material for use asan anti-drip agent. Either method may be used to produce an encapsulatedfluoropolymer. Antidrip agents can be used in amounts of 0.1 to 5percent by weight, based on the total weight of the sulfonate end-cappedpolycarbonate and any added polycarbonate.

While it is contemplated that other resins may be used in thethermoplastic compositions described herein, the sulfonate end-cappedpolycarbonates are particularly suited for use in thermoplasticcompositions that contain only polycarbonate-type resins as describedherein (homopolycarbonates, siloxane-copolycarbonates, copolyestercarbonates, polycarbonate copolymers with soft blocks, and combinationsthereof). Thus, in an embodiment, a thermoplastic composition consistsessentially of a polycarbonate resin and 0.001 to 500 millimoles perkilogram (mmol/Kg), more specifically 0.01 to 50 mmol/Kg, even morespecifically 0.1 to 5 mmol/kg of a sulfonate end-capped polycarbonate,based on the combined weight of the polycarbonate resin and thesulfonate end-capped polycarbonate, excluding any other additives and/orfillers. In another embodiment, a thermoplastic composition consistsessentially of a polycarbonate composition comprising 0 to 99.9 wt % ofa polycarbonate and of 0.1 to 100 wt % of a sulfonate end-cappedpolycarbonate. In another embodiment, a thermoplastic compositionconsists essentially of a polycarbonate composition comprising 20 to 99wt % of a polycarbonate and 1 to 80 wt % of a sulfonate end-cappedpolycarbonate. In another embodiment, a thermoplastic compositionconsists essentially of a polycarbonate composition comprising 50 to 98wt % of a polycarbonate and 2 to 50 wt % of a sulfonate end-cappedpolycarbonate. In still another embodiment, a thermoplastic compositionconsists essentially of a polycarbonate composition comprising 60 to 95wt % of a polycarbonate and 5 to 40 wt % of a sulfonate end-cappedpolycarbonate. In still another embodiment, a thermoplastic compositionconsists essentially of a polycarbonate composition comprising 70 to 91wt % of a polycarbonate and 9 to 30 wt % of a sulfonate end-cappedpolycarbonate. Each of the foregoing wt % values are based on thecombined weights of the polycarbonate and the sulfonate end-cappedpolycarbonate, wherein each of the foregoing weight percentages is basedon the combined weight of the polycarbonate and the sulfonate end-cappedpolycarbonate, excluding any other additives and/or fillers.

In another embodiment, the thermoplastic composition further comprises0.001 to 1 wt % of an ionizing radiation stabilizing compound, based onthe combined weight of the polycarbonate and the sulfonate end-cappedpolycarbonate. In another specific embodiment, the thermoplasticcomposition comprises 0.001 to 1 wt % of hydrolysis stabilizer, based onthe combined weight of the polycarbonate and the sulfonate end-cappedpolycarbonate.

In a further embodiment, the thermoplastic composition may comprise anadditive selected from impact modifier, filler, antioxidant, heatstabilizer, light stabilizer, ultraviolet light absorber, plasticizer,mold release agent, lubricant, antistatic agent, pigment, dye, flameretardant, anti-drip agent, or a combination comprising at least one ofthese.

The thermoplastic composition may be manufactured by methods generallyavailable in the art, for example, in one embodiment, in one manner ofproceeding, powdered polycarbonate, sulfonate end-capped polycarbonate,and other optional components including ionizing radiation stabilizingadditiver are first blended, in a HENSCHEL-Mixer® high speed mixer.Other low shear processes including but not limited to hand mixing mayalso accomplish this blending. The blend is then fed into the throat ofan extruder via a hopper. Alternatively, one or more of the componentsmay be incorporated into the composition by feeding directly into theextruder at the throat and/or downstream through a sidestuffer. Wheredesired, the sulfonate end-capped polycarbonate and any desired polymerand/or additives may also be compounded into a masterbatch and combinedwith a desired polymeric resin and fed into the extruder. The extruderis generally operated at a temperature higher than that necessary tocause the composition to flow. The extrudate is immediately quenched ina water batch and pelletized. The pellets, so prepared, when cutting theextrudate may be one-fourth inch long or less as desired. Such pelletsmay be used for subsequent molding, shaping, or forming.

In a specific embodiment, a method of preparing a thermoplasticcomposition comprises melt combining a polycarbonate and a sulfonateend-capped polycarbonate. The melt combining can be done by extrusion.In an embodiment, the proportions of sulfonate end-capped polycarbonateand any added polycarbonate are selected such that the opticalproperties of the thermoplastic composition are maximized whilemechanical performance is at a desirable level. In a further specificembodiment, an ionizing radiation stabilizing additive is combined withthe sulfonate end-capped polycarbonate and any added polycarbonate tomake the thermoplastic composition. In a further specific embodiment, ahydrolysis stabilizer is also included. In an embodiment, theproportions of polycarbonate, sulfonate end-capped polycarbonate, andwhere desired, ionizing radiation stabilizing additive and/or hydrolysisstabilizer, are selected such that the optical properties of thethermoplastic composition are maximized while mechanical performance isat a desirable level.

In a specific embodiment, the extruder is a twin-screw extruder. Theextruder is typically operated at a temperature of 180 to 385° C.,specifically 200 to 330° C., more specifically 220 to 300° C., whereinthe die temperature may be different. The extruded thermoplasticcomposition is quenched in water and pelletized.

Shaped, formed, or molded articles comprising the thermoplasticcompositions are also provided. The thermoplastic compositions may bemolded into useful shaped articles by a variety of means such asinjection molding, extrusion, rotational molding, blow molding andthermoforming. In a specific embodiment, molding is done by injectionmolding. Desirably, the thermoplastic composition has excellent moldfilling capability and is useful to form articles such as, for example,bottles, syringes, dialysis fittings, tubing, sample vials, blood bags,petri dishes, beakers, centrifuge tubes, spatulas, connectors, trocars,stopcocks, luer locks, Y-sites, catheters, oxygenator housings, trays,dental instruments, pipettes, glucose meters, inhalers, and the like.

The thermoplastic composition is further illustrated by the followingnon-limiting examples.

All thermoplastic compositions were compounded on a Werner & Pfleidererco-rotating twin screw extruder (Length/Diameter (L/D) ratio=30/1,vacuum port located near die face). The twin-screw extruder had enoughdistributive and dispersive mixing elements to produce good mixing ofthe polymer compositions. The compositions are subsequently moldedaccording to ISO 294 on a Husky or BOY injection molding machine.Compositions were compounded and molded at a temperature of 250 to 330°C., though it will be recognized by one skilled in the art that themethod is not limited to these temperatures.

The thermoplastic compositions are tested for the following properties.Yellowness Index (YI) for laboratory scale samples was determined usinga Gretag Macbeth Color System at an illuminant observer of C/2°, inaccordance with ASTM D1925-70 on 3.2±0.12 millimeter thick moldedplaques. The increase in YI (dYI) is calculated by subtracting theyellowness index value of a non-irradiated sample from that of anirradiated sample of the same composition. Molecular weight change wastested under conditions of either heat at 80° C. in a dry, nitrogenpurged oven, or heat and moisture at 80° C. and 80% relative humidity(80/80), according to the following procedure: a 100 gram sample of thepolycarbonate was placed in either an oven at 80° C. plus or minus 3° C.having a relative humidity of 80% established by introduction of watervapor; or alternatively, in an oven that was preheated to 80° C., andhad a stream of dry air purged through the chamber. The sample wasmaintained at the desired temperature for 2 weeks (wk). The sample wasremoved from the oven, dissolved in methylene chloride, diluted to aconcentration of 1 mg/ml, and was analyzed by gel permeationchromatography using a crosslinked styrene-divinylbenzene column andcalibrated against polycarbonate standards. The difference in weightaveraged molecular weight is determined from a comparison of the weightaveraged molecular weights of a sample and control.

Polycarbonate compositions for the examples (abbreviated Ex. in thefollowing tables) and comparative examples (also abbreviated CEx.) wereprepared using the components shown in Table 1.

TABLE 1 BPA-PC BPA polycarbonate resin (MVR = GE Plastics 17.5 g/10 minat 300° C.) TPC-1 Tosyl end-capped poly(bisphenol- See Procedures, belowA carbonate), (Mw = 24,600, Mw/Mn = 2.4) TPC-2 Tosyl end-cappedpoly(bisphenol- See Procedures, below A carbonate), (Mw = 25,000, Mw/Mn= 2.0)) MPD 2-Methyl-2,4-pentanediol Aldrich Chemical Co. (hexyleneglycol), 99% purity PETS Pentaerythritol tetrastearate FACI Farasco,(mold release agent) Genova, Italy I-168 IRGAFOS ® 168 (Tris (2,6- CibaSpecialty di-tert-butylphenyl)phosphite) Chemicals (antioxidant)ADR-4368 JONCRYL ® ADR-4368 Johnson Polymer hydrolysis stabilizer

The polycarbonate resins and additives were blended in a powder mixer,extruded on a twin-screw extruder as described above, and injectionmolded into flat, rectangular plaques, using the equipment describedabove. The sulfonate end-capped polycarbonate, tosyl end-cappedpoly(bisphenol-A carbonate) (TPC), was prepared using either of the twomethods described below.

Tosyl end-capped poly(bisphenol-A carbonate), Method 1 (TPC-1). Thefollowing were added into a 70 L CSTR equipped with an overheadcondenser and a recirculation pump with a flow rate of 40 L/minute:4,4-bis-(hydroxyphenyl)-2,2-propane (bisphenol-A, BPA) (5000 g, 21.9mol); TsCl (167.2 g, 0.88 mol); triethylamine (45.9 ml, 0.33 mol);methylene chloride (27 kg); and de-ionized water (14 kg). The mixturewas charged with phosgene (2876 g, 140 g/min, 29 mol). During theaddition of phosgene, base (50 wt % NaOH in deionized water) wassimultaneously charged to the reactor to maintain the pH of the reactionbetween 9 and 11. After the complete addition of phosgene, the reactionwas purged with nitrogen gas, and the organic layer was extracted. Theorganic extract was washed once with dilute hydrochloric acid (HCl), andsubsequently washed with de-ionized water three times. The TPC waspurified by precipitation from the methylene chloride organic layer byaddition to methanol. The TPC polymer was dried in an oven at 110° C.before analysis. The Mw of the polycarbonate was measured by GPC using acrosslinked styrene-divinylbenzene column to be 24,600 amu (referencedto polycarbonate standards), with a polydispersity (Mw/Mn)=2.4.

Tosyl end-capped poly(bisphenol-A carbonate), Method 2 (TPC-2). Thefollowing were added into a 70 L CSTR equipped with an overheadcondenser and a recirculation pump with a flow rate of 40 L/minute: (a)4,4-bis-(hydroxyphenyl)-2,2-propane (bisphenol-A, BPA) (4540 g, 19.9mol); (b) Tosyl chloride (TsCl) (166.7 g, 0.88 mol); (c) triethylamine(30 mL, 0.22 mol); (d) methylene chloride (16 L); (e) de-ionized water(14 L), (f) sodium gluconate (10 g), and methyl-tributyl ammoniumchloride (75 wt % solution in water, 32 g). The reaction was allowed tostir for 10 minutes and the pH was maintained at pH between 8 and 10 bythe addition of 86 g of 50% NaOH solution. The mixture was charged withphosgene (2961 g, 40 g/min, 29.9 mol). During the addition of phosgene,base (50 wt % NaOH in deionized water) was simultaneously charged to thereactor to maintain the pH of the reaction between 9 and 11. After thecomplete addition of phosgene, the reaction was purged with nitrogengas, and the organic layer was extracted. The organic extract was washedonce with dilute hydrochloric acid (HCl), and subsequently washed withde-ionized water three times. The organic layer was precipitated frommethylene chloride into hot steam. The polymer was dried in an oven at110° C. before analysis. The Mw of the polycarbonate was measured by GPCusing a crosslinked styrene-divinylbenzene column to be 25,000 amu(referenced to polycarbonate standards), with a polydispersity(Mw/Mn)=2.0.

Comparative Examples 1-3 and Examples 1-7. Examples 1-7 were prepared bycombining BPA-PC polycarbonate resin, either TPC-1 or TPC-2, and MPD,according to the ratios described in Table 2, below, and melt blendingusing the above-described processing conditions. Comparative Examples1-3 were prepared as described above using polycarbonate resin in placeof the TPC-1 or TPC-2 additive charges, and 0.15 wt % MPD. In addition,in Examples 3, 5, and 7, and Comparative Example 3, a hydrolysisstabilizer (ADR-4368) was included. All examples and comparativeexamples contain 0.27 wt % PETS (plasticizer/mold release agent) and0.027 wt % Irgafos® I-168 (antioxidant).

The pellets were injection molded into rectangular 3.2 mm thick plaquesthat were placed into a sealed package to prevent contact with light andmoisture. The plaques were then subjected to high energy irradiation atnominal doses of 25, 50, or 75 kiloGrays (kGy) (common forsterilization; actual doses are reported in the tables), andsubsequently measured for the change in yellowness index (dYI) accordingto the method described above which uses YI measurements according toASTM D1925-70. Identical sets of irradiated plaques were also placedinto an oven for environmental exposure at either 80° C. or acombination of 80° C. and 80% humidity, using the process describedabove. Table 2 shows the dYI data for the examples after exposure tohigh energy gamma irradiation. The compositions and irradiation andenvironmental exposure data are shown in Table 2, below.

TABLE 2* TPC Load Hydr. Hydr. Stab. dYI dYI dYI dYI % Mw loss % Mw lossTPC (wt %) Stab. Load (wt %) (30 kGy)^(1,2) (51 kGy)^(1,2) (81kGy)^(1,2) (83 kGy)^(1,2) (51 kGy)^(1,3,5) (51 kGy)^(1,4,5) CEx. 1 — 0 —0 — 15.1 — 45.4 7 5.4 CEx. 2 — 0 — 0 7.8 15.5 24.8 — — — CEx. 3 — 0 ADR4368 0.25 — 14.7 — 36.4 8.2 5.4 Ex. 1 TPC-1 10 — 0 6.0 10.8 16.5 — — —Ex. 2 TPC-1 20 — 0 5.3 9.7 15.5 — — — Ex. 3 TPC-1 20 ADR 4368 0.25 6.211.5 16.8 — — — Ex. 4 TPC-2 10 — 0 6.6 8.2 — 17.4 34.2 15 Ex. 5 TPC-2 10ADR 4368 0.25 — 8.7 — 17.4 34.2 14 Ex. 6 TPC-2 20 — 0 5.6 7.1 — 12.744.6 18 Ex. 7 TPC-2 20 ADR 4368 0.25 5.9 7.3 — 11.7 42 18.6 *All samplescontain 0.15 wt % of MPD, 0.027 wt % of I-168, and 0.27 wt % of PETS.¹Irradiation doses reported in Table 2 in kiloGrays (kGy) are actualdoses. A 25 kGy nominal dose gave a 30 kGy actual dose; a 50 kGy nominaldose gave a 51 kGy actual dose; and a 75 kGy nominal dose gave actualdoses of 81 and 83 kGy for different runs. ²dYI values represent gain inYI compared to before-irradiation samples. A negative value indicates aloss in YI. ³Environmental exposure conditions: 80° C., 80% relativehumidity, 2 weeks. ⁴Environmental exposure conditions: 80° C., <5%relative humidity, 2 weeks. ⁵% Mw loss represents loss in value comparedto before-irradiation samples. A negative value indicates a loss in YI.

Difunctional aromatic sulfonate end-capped polycarbonates TPC-1 andTPC-2, in which the tosylate end groups are separated by a mediummolecular weight bisphenol-A polycarbonate, were examined for resistanceto increased dYI. Each of the polycarbonate compositions containing thesulfonate end groups (Examples 1-7) displays a marked effect on the dYIcompared to the Comparative Examples 1-3, wherein the TPC-containingcompositions have dYI values that are significantly lower than those ofthe comparative examples without TPC. Examples 1 and 4 (each with 10 wt% TPC) generally show slightly less resistance to yellowing thanExamples 2 and 6 (each with 20 wt % TPC). Of these, Example 6, preparedusing TPC-2, appears to have slightly better resistance to yellowingthan Example 2, prepared using with TPC-1. Examples 3, 5, and 7, eachhaving TPC with 0.25 wt % ADR-4368, overall show comparable performanceto their respective counterpart examples without hydrolysis stabilizer(Examples 2, 4, and 6, respectively). Within these samples, at a fixedamount of hydrolysis stabilizer, resistance to yellowing dYI at highergamma ray doses (81 and 83 kGy) is better with increasing TPC content,wherein best resistance to yellowing (dYI) at 83 kGy is seen in Example7. Generally, the epoxide additives did not significantly improve ordegrade the hydrolytic stability of the polycarbonate resin. Withoutwishing to be bound by theory, it is believed the epoxide moieties maybe reacting with other high-energy species that are formed during thegamma ray irradiation of the polycarbonate compositions.

Generally, the data above show that low color or colorless articles(i.e., having low or no added colorant) having good optical propertiessuch as low yellowness and where desired, high transparency, may beprepared using the thermoplastic compositions described herein. Sucharticles can maintain these desired properties after irradiation at highdoses (up to 83 kGy) of gamma radiation.

Compounds are described herein using standard nomenclature. A dash (“-”)that is not between two letters or symbols is used to indicate a pointof attachment for a substituent. For example, —CHO is attached throughthe carbon of the carbonyl (C═O) group. The singular forms “a,” “an,”and “the” include plural referents unless the context clearly dictatesotherwise. The endpoints of all ranges reciting the same characteristicor component are independently combinable and inclusive of the recitedendpoint. All references are incorporated herein by reference. The terms“first,” “second,” and the like herein do not denote any order,quantity, or importance, but rather are used to distinguish one elementfrom another. The notation “±0.012 mm” means that the indicatedmeasurement can be from an amount that is minus 0.012 mm to an amountthat is plus 0.012 mm of the stated value.

While typical embodiments have been set forth for the purpose ofillustration, the foregoing descriptions should not be deemed to be alimitation on the scope herein. Accordingly, various modifications,adaptations, and alternatives may occur to one skilled in the artwithout departing from the spirit and scope herein.

1. A thermoplastic composition comprising: a sulfonate end-cappedpolycarbonate of formula:Z-S(O)₂—O-(-L-)_(m)-O—S(O)₂-Z wherein each Z is independently an alkylor aryl group, wherein -(-L-)_(m)- is a polycarbonate linking group withm units of linking unit L, and wherein m is at least one, and anionizing radiation stabilizing additive comprising2-methyl-2,4-pentanediol (hexylene glycol).
 2. The thermoplasticcomposition of claim 1, comprising 0.001 to 500 mmol/Kg of the sulfonateend-capped polycarbonate, based on the total weight of the thermoplasticcomposition.
 3. The thermoplastic composition of claim 1, comprising ablend of a polycarbonate and the sulfonate end-capped polycarbonate,wherein the sulfonate end-capped polycarbonate is used in an amount of0.1 to 100 wt %, based on the total weight of the polycarbonate andsulfonate end-capped polycarbonate, with the proviso that the amount andtype of sulfonate end-capped polycarbonate used is selected so that theoverall concentration of sulfonate end groups is not greater than amolar concentration of 500 millimoles per kilogram (mmol/Kg), and is notless than 0.001 mmol/Kg, of the total weight of the sulfonate end-cappedpolycarbonate and any added polycarbonate.
 4. The thermoplasticcomposition of claim 1, wherein m is 1 to
 500. 5. The thermoplasticcomposition of claim 1, wherein each Z is a C₁-C₂₀ alkyl group,substituted C₁-C₂₀ alkyl group, C₆-C₂₀ aryl group, or substituted C₆-C₂₀aryl group.
 6. The thermoplastic composition of claim 1, wherein Lcomprises carbonate units, ester units, poly(arylene ether) units, softblock units, or a combination comprising at least one of these; andwherein at least one L is a carbonate unit.
 7. The thermoplasticcomposition of claim 6 wherein the poly(arylene ether) unit has theformula:—(—Ar¹—X—Ar¹—O—)_(n)—Ar¹—X—Ar¹— wherein n is 0 to 200, wherein each Ar¹is independently a substituted C₆-C₂₀ arylene group or unsubstitutedC₆-C₂₀ arylene group; and wherein X is a bridging radical having one ortwo atoms that separate the Ar¹ groups.
 8. The thermoplastic compositionof claim 6, wherein soft block units include polysiloxane units,polyalkylene oxide units, poly(alkylene ester) units, polyolefin units,or a combination comprising at least one of these.
 9. The thermoplasticcomposition of claim 1, wherein the ionizing radiation stabilizingadditive further comprises an aliphatic alcohol, an aromatic alcohol, analiphatic diol, an aliphatic polyol, an aliphatic ether, an esters, adiketone, an alkene, a thiol, thioethers, a cyclic thioether, a sulfone,a dihydroaromatic, a diether, a nitrogen compound, or a combinationcomprising at least one of the foregoing.
 10. The thermoplasticcomposition of claim 9 wherein the aliphatic diol has the structure:HO—(C(A′)(A″))_(c)-S—(C(B′)(B″))_(d)—OH wherein A′, A″, B′, and B″ areeach individually H or C₁-C₆ alkyl; and wherein S is C₁-C₂₀ alkyl,C₂-C₂₀ alkyleneoxy, C₃-C₆ cycloalkyl, or C₃-C₆ substituted cycloalkyl;and wherein c and d are each 0 or 1, with the proviso that, where c andd are each 0, S is selected such that both —OH groups are not connecteddirectly to a single common carbon atom.
 11. The thermoplasticcomposition of claim 1, further comprising hydrolysis stabilizer, impactmodifier, filler, antioxidant, heat stabilizer, light stabilizer,ultraviolet light absorber, plasticizer, mold release agent, lubricant,antistatic agent, pigment, dye, flame retardant, anti-drip agent, or acombination comprising at least one of these.
 12. The thermoplasticcomposition of claim 1, wherein the sulfonate end-capped polycarbonateincludes sulfonate end-capped polycarbonate homopolymers, sulfonateend-capped polycarbonate copolymers, sulfonate end-cappedpolyester-polycarbonate, sulfonate end-cappedpolysiloxane-polycarbonate, sulfonate end-cappedpolysiloxane-co-(polyester-polycarbonate), sulfonate end-cappedpoly(aiylene ether)-co-polycarbonate, sulfonate end-capped poly(aryleneether)-co-(polyester-polycarbonate), sulfonate end-capped poly(alkyleneester)-co-polycarbonate, sulfonate end-capped poly(alkyleneester)-co-(polyester-polycarbonate), sulfonate end-capped poly(alkyleneether)-co-polycarbonate, sulfonate end-capped poly(alkyleneether)-co-(polyester-polycarbonate), sulfonate end-cappedpolyolefin-co-polycarbonate, sulfonate end-cappedpoly(olefin)-co-(polyester-polycarbonate), or a combination comprisingat least one of these.
 13. The thermoplastic composition of claim 1,wherein the sulfonate end-capped polycarbonate is tosyl end-cappedpoly(bisphenol-A carbonate).
 14. The thermoplastic composition of claim1, wherein a molded article having a thickness of 3.2± 0.12 millimetersand consisting of the sulfonate end-capped polycarbonate, apolycarbonate resin, and an effective amount of each of an aliphaticdiol, a mold-release agent, and an antioxidant has, after exposure to atotal gamma radiation dose of 83 kGy and when measured according to ASTMD1925-70, an increase in yellowness index (dYI) of less than or equal to36, when compared to the unexposed article.
 15. A thermoplasticcomposition comprising: a sulfonate end-capped polycarbonate of formula:Z-S(O)₂—O-(-L-)_(m)-O—S(O)₂-Z wherein each Z is independently an alkylor aryl group, wherein -(-L-)_(m)- is a polycarbonate linking group withm units of linking unit L, and wherein m is at least one; wherein amolded article having a thickness of 3.2±0.12 millimeters and consistingof the sulfonate end-capped polycarbonate, a polycarbonate resin, and aneffective amount of each of an aliphatic diol, a mold-release agent, andan antioxidant has, after exposure to a total gamma radiation dose of 83kGy and when measured according to ASTM D1925-70, an increase inyellowness index (dYI) of less than or equal to 36, when compared to theunexposed article.
 16. A thermoplastic composition comprising: asulfonate end-capped polycarbonate of formula:Z-S(O)₂—O-(-L-)_(m)-O—S(O)₂-Z wherein each Z is independently an alkylor aryl group, and -(-L-)_(m)- is a polycarbonate linking group with munits of linking unit L, wherein m is at least one; and a polycarbonate,wherein the sulfonate end-capped polycarbonate is present in an amountof 0.1 to 100 wt %, based on the total weight of the sulfonateend-capped polycarbonate and any added polycarbonate, with the provisothat the amount and type of sulfonate end-capped polycarbonate used isselected so that the overall concentration of sulfonate end groups isnot greater than a molar concentration of 500 millimoles per kilogram(mmol/Kg), and is not less than 0.001 mmol/Kg, of the total weight ofthe thermoplastic composition.
 17. A thermoplastic compositioncomprising: a sulfonate end-capped polycarbonate of formula:Z-S(O)₂—O-(-L-)_(m)-O—S(O)₂-Z wherein each Z is independently an alkylor aryl group, and -(-L-)_(m)- is a polycarbonate linking group with munits of linking unit L, wherein m is at least one; and a polycarbonate,wherein a molded article having a thickness of 3.2±0.12 millimeters andconsisting of the sulfonate end-capped polycarbonate, the polycarbonate,and an effective amount of each of an aliphatic diol, a mold-releaseagent, and an antioxidant has, after exposure to a total gamma radiationdose of 83 kGy and when measured according to ASTM D1925-70, an increasein yellowness index (dYI) of less than or equal to 36, when compared tothe unexposed article.
 18. A method of preparing a sulfonate end-cappedpolycarbonate, comprising condensing: a dihydroxy compound, a reactivesulfonic acid derivative, and an activated carbonyl compound, in abiphasic medium at a pH of about 9 to about 11 and in the presence of aphase transfer catalyst having the formula (R)₄Q⁺X, wherein each R isthe same or different, and is a C₁₋₁₀ alkyl group; Q is a nitrogen orphosphorus atom; and X is a halogen atom or a C₁₋₈ alkoxy group or C₆₋₁₈aryloxy group.
 19. The method of claim 18 wherein the activated carbonylcompound is phosgene, diphosgene, triphosgene, a dichloroformate, or acombination comprising at least one of these.
 20. The method of claim 18wherein the dihydroxy compound comprises a dihydroxy aromatic compound,a dihydroxy poly(arylene ether), a dihydroxy soft-block compound, or acombination comprising at least one of these.
 21. The method of claim18, wherein the activated carbonyl compound is phosgene, wherein thephase transfer catalyst is methyl tri-n-butyl ammonium chloride; whereinthe dihydroxy compound is bisphenol-A, and wherein the reactive sulfonicacid derivative is p-toluenesulfonyl chloride.
 22. The method of claim18 wherein the sulfonate end-capped polycarbonate prepared by the methodhas a polydispersity (Mw/Mn) of less than or equal to 2.4, as determinedusing molecular weights determined by GPC using a crosslinkedstyrene-divinylbenzene column calibrated with polystyrene orpolycarbonate standards.
 23. The method of claim 18 wherein thesulfonate end-capped polycarbonate prepared by the method has less than5 percent by weight of residual reactive sulfonic acid derivative basedon the total weight of the sulfonate end-capped polycarbonate.
 24. Themethod of claim 18, wherein the sulfonate end-capped polycarbonate hassulfonate end groups, and wherein the sulfonate end groups are presentin amount of 0.01 to 10 mole-percent (mol %), per the total number ofmoles of repeating unit L present in the sulfonate end-cappedpolycarbonate.
 25. A method of making a thermoplastic compositioncomprising melt-blending: a sulfonate end-capped polycarbonate offormula:Z-S(O)₂—O-(-L-)_(m)-O—S(O)₂-Z wherein each Z is independently an alkylor aryl group, and -(-L-)_(m)- is a polycarbonate linking group with munits of linking unit L, wherein m is at least one; and a polycarbonate,wherein a molded article having a thickness of 3.2±0.12 millimeters andconsisting of the sulfonate end-capped polycarbonate, the polycarbonate,and an effective amount of each of an aliphatic diol, a mold-releaseagent, and an antioxidant has, after exposure to a total gamma radiationdose of 83 kGy and when measured according to ASTM D1925-70, an increasein yellowness index (dYI) of less than or equal to 36, when compared tothe unexposed article.
 26. An article comprising the thermoplasticcomposition of claim
 1. 27. A thermoplastic composition comprising: ablend of a polycarbonate, and a sulfonate end-capped polycarbonate offormula:Z-S(O)₂—O-(-L-)_(m)-O—S(O)₂-Z wherein each Z is independently an alkylor aryl group, -(-L-)_(m)- is a polycarbonate linking group with m unitsof linking unit L, and m is at least one, wherein the amount and type ofsulfonate end-capped polycarbonate is selected so that the overallconcentration of sulfonate end groups is not greater than a molarconcentration of 500 millimoles per kilogram (mmol/Kg), and is not lessthan 0.001 mmol/Kg, of the total weight of the sulfonate end-cappedpolycarbonate and the polycarbonate.
 28. The thermoplastic compositionof claim 1, comprising a blend of a polycarbonate and the sulfonateend-capped polycarbonate, wherein the sulfonate end-capped polycarbonateis used in an amount of 1 to 80 wt %, based on the total weight of thepolycarbonate and sulfonate end-capped polycarbonate, with the provisothat the amount and type of sulfonate end-capped polycarbonate used isselected so that the overall concentration of sulfonate end groups isnot greater than a molar concentration of 500 millimoles per kilogram(mmol/Kg), and is not less than 0.001 mmol/Kg, of the total weight ofthe sulfonate end-capped polycarbonate and any added polycarbonate.